I'm trying to understand how/why centering predictors in a 2 predictor regression model would change the coefficients  Lets say I have 2 centered predictors and an interaction term, predicting a continuous Y variable that is not centered, and I have gone through the process of calculating all the regression coefficients (b0-3).  Now, the question is, if I were to uncenter the 2 predictors, how would the coefficients change (if at all)?  From my understanding, the distribution of data points would not change, nor would the regression plane. However, by centering/uncentering we change the (X1, X2, Y) value of each datapoint. I don't believe this would change the b3 interaction coefficient because the relationship between the simple slopes would not be affected. The coefficients for the intercept and the 2 predictors, however, should change because we've essentially changed the scale for each of the predictors.  Can anyone shed some light on why/how this happens? and how do you determine the magnitude/direction of these changes?

I have a question related to multiple regression and interaction, inspired by this CV thread:    When checking for a moderation effect I do center my independent variables and multiply the centered variables in order to calculate my interaction term. Then I run my regression analysis and check for main and interaction effects, which may show the moderation.  If I redo the analysis without centering, apparently the coefficient of determination ($R^2$) does not change but the regression coefficients ($\beta$s) do. That seems clear and logical.  What I do not understand: The p-values of the main effects change substantially with centering, although the interaction does not (which is right). So my interpretation of main effects could change dramatically - just determined by centering or not. (It's is still the same data, in both analyses!)  Can somebody clarify? - Because that would mean that the option to center my variables would be mandatory and everybody should do it in order to get the same results with the same data.    Thanks a lot for distributing to that problem and your comprehensive explanations. Be assured that your help is very much appreciated!  For me, the biggest advantage of centering is to avoid multicollinearity. It is still quite confusing to establish a rule, whether to center or not. My impression is, that most of the resources suggest to center, although there are some "risks" when doing it. Again I want to put out the fact, that 2 researchers dealing with the same material and data might conclude different results, because one does centering and the other does not. I just read some part of a book by Bortz (he was a Professor and kind of a Statistics Star in Germany and Europe), and he does not even mention that technique; just points out to be careful in interpreting main effects of variables when they are involved in interactions.  After all, when you conduct a regression with one IV, one moderator (or second IV) and a DV, would you recommend to center or not?


I need to define and use a "3-dimensional" dictionary.  I don't fully understand dictionaries, so I'm sure what I'm doing is, at best, flawed ... and probably just outright dumb. Code: # Set up and initialize two-dimensional dict maxR = 3 R = {"one": [0] * maxR,      "two": [0] * maxR      }  # Set up and initialize three-dimensional dict maxE = 4 E = {"alpha": [[0] * maxE] * maxR,      "beta" : [[0] * maxE] * maxR     }  # change some individual values R ["one"][2] = 11 R ["two"][0] = 13 E ["alpha"][2][3] = 17 E [("beta", 1, 2)] = 29  # Print out contents for i in range (maxR):     print ("R [one][", i, ", ] = ", R ["one"][i]) for i in range (maxR):     print ("R [two][", i, ", ] = ", R ["two"][i]) print () for i in range (maxR):     for j in range (maxE):         print ("E [alpha][", i, "] [", j, "] = ", E ["alpha"][i][j]) for i in range (maxR):     for j in range (maxE):         print ("E [beta][", i, "] [", j, "] = ", E ["beta"][i][j])  Results: R [one][ 0 , ] =  0    R [one][ 1 , ] =  0 R [one][ 2 , ] =  11 R [two][ 0 , ] =  13 R [two][ 1 , ] =  0 R [two][ 2 , ] =  0  E [alpha][ 0 ] [ 0 ] =  0 E [alpha][ 0 ] [ 1 ] =  0 E [alpha][ 0 ] [ 2 ] =  0 E [alpha][ 0 ] [ 3 ] =  17 E [alpha][ 1 ] [ 0 ] =  0 E [alpha][ 1 ] [ 1 ] =  0 E [alpha][ 1 ] [ 2 ] =  0 E [alpha][ 1 ] [ 3 ] =  17 E [alpha][ 2 ] [ 0 ] =  0 E [alpha][ 2 ] [ 1 ] =  0 E [alpha][ 2 ] [ 2 ] =  0 E [alpha][ 2 ] [ 3 ] =  17 E [beta][ 0 ] [ 0 ] =  0 E [beta][ 0 ] [ 1 ] =  0 E [beta][ 0 ] [ 2 ] =  29 E [beta][ 0 ] [ 3 ] =  0 E [beta][ 1 ] [ 0 ] =  0 E [beta][ 1 ] [ 1 ] =  0 E [beta][ 1 ] [ 2 ] =  29 E [beta][ 1 ] [ 3 ] =  0 E [beta][ 2 ] [ 0 ] =  0 E [beta][ 2 ] [ 1 ] =  0 E [beta][ 2 ] [ 2 ] =  29 E [beta][ 2 ] [ 3 ] =  0  The two-dimensional version ("R") works as I expected.  However the three-dimensional version ("E") does not -- it appears to set values in a slice rather than an individual element. Note the "17" and "29" values above.  What am I doing wrong?  [note: my actual application is not homogeneous so I can't use arrays]

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


What is the best way to show a folder structure using Stack Overflow formatting?  Here's how I have written it now, I wish I could do it better:  >_rels >customXML >docProps >word //this folder contains most of the files that control the content of yhe document     >_rels          >document.xml.rels //this document tells word where the images are situated     >media  //This folder contains all images embedded in the word     >theme     >document.xml //Is the actual content of the document     >header1.xml //Is the content of the header >[Content_Types].xml

I'm always looking for the best way to represent a file structure on my posts.  I generally use this one:  Project  |  +-- file 1  |      +-- dir 2  |  |    |  +-- file 2.1  |      +-- dir 3  |  |    |  +-- file 3.1  |  +-- file 3.2  |      +-- dir 4  |  |    +  |-- dir 4.1   Is there a real convention for those representations? Is there any script (Windows, Linux or web app service) that provide formatting?  Any advice / tool / recommendation / ISO ( ? ;) ) would be appreciated.  Some examples:


Is there a billing system that exists where I can have recurring billing every month, and change the amount the client is charged each month using code? For example, one month a user uses our service for one week and is charged $10, but the next week they use the service for 3 weeks and are charged $30, then the following month they use it for  weeks and are charged $20. Every system I've looked at you must manually change this value, and I was wondering if there was a system that allowed you to automate this process. Any help would be greatly appreciated, thanks!

Hi i'm looking for a payment gateway that can do recurring billing that changes month to month.  Fogbugz do this, they charge based on how many active users there were that month. All of the APIs that i've found only let you set a fixed amount and it's difficult/impossible to vary the subscription amount month to month.  Has anyone come across any services that do this?


It seems that multiple regression is a better way to do analysis. For example,the ANOVA simply gives t-value (or F-value for two or more variables) and does not indicate magnitude of effect. Contrary-wise, the regression analysis indicates both the t-value(s) as well as magnitude of regression coefficients. Does that mean we should discard ANOVA completely.

I read that ANOVA and linear regression are the same thing. How can that be, considering that the output of ANOVA is some $F$ value and some $p$-value based on which you conclude if the sample means across the different samples are same or different.  But assuming the means are not equal (reject null hypothesis), ANOVA tells you nothing about the coefficients of the linear model. So how is linear regression the same as ANOVA?


I am moving from Malaysia to the US, and planning to bring my desktop computer with me. I plan to pack it in my checked-in luggage. Will the computer risk being damaged? Any precaution should I take to reduce this risk? Will there be any trouble with the airline or immigration about bringing computer?

On an upcoming trip, I will be taking a desktop computer and monitor as checked luggage (on a United/Continental flight). What should I be aware of when doing this? What needs to be done to properly protect all the components? Are there any airline policies I should be aware of?


Editor's note: While this question is specifically about copying a file reference to the clipboard, its generic title led to answers about how to copy / get  text.  As an Emacs user on Windows who often attaches files in mails, I have been looking for a utility to copy a file (not its contents) to the clipboard, just as windows explorer does on righclick/copy).  I just found  right here on SO which uses System.Windows.Forms.Clipboard` in a small program to do exactly that. But it is in C#, for which I don't have immediate access to a compiler. So I am wondering if this can be done and how.   I saw several references such as  that the clipboard is not accessible in VBScripting, but msdn  documentation for VB so I am risking the question.  I have never written a VBScript before but I did try a few things before asking, starting with running a copy pasted a "Hello world" and then various combinations of CreateObject etc.   Update: I need to call , so I do not think I can use ClipboardData as suggested by the answers, it does not have this method.   Update for visitors  The solution I ended up using was to compile the C# itself, I did not know I already had a compiler.  Another update for visitors  is what I am now using, quite happily.

I am looking for a method to place some text onto the clipboard with .  The VBScript in question will be deployed as part of our login script.  I would like to avoid using anything that isn't available on a clean Windows XP system.  Edit: In answer to the questions about what this is for.  We wanted to encourage users inside our organization to use the file server to transfer documents instead of constantly sending attachments by email.  One of the biggest barriers to this is that it isn't always obvious to people what the correct network path is to a file/folder.  We developed a quick script, and attached it to the Windows context menu so that a user can right click on any file/folder, and get a URL that they can email to someone within our organization.  I want the URL displayed in the dialog box to also be placed onto the clipboard.


I am in possession of a long PDF file. On each and every page of this file there is an annoying watermark/logo that I wish to remove. The printing shop unlawfully added their own logo on somebody else's work while scanning the document.   is a screenshot of a random page of the document. I circled in red the watermark that I'm trying to remove. Thanks.  EDIT: this question is not a duplicate. The other answers are literally not working in my case. The watermark in my case is part of the page SCAN, it is not metadata in the pdf file. Please read the questions before closing them.

I thought this would be a simple task, but it turned out the other way.  The watermark is the very same (overlapping, but transparent) image on every single page. I created the PDF file myself (so no copyright worries here) using PDFCreator 0.9.8.  I have already tried my friend's Adobe Acrobat Pro, but it didn't work. It tries to remove it, but it can't. I tried to remove header/footer, etc., but the watermark just won't disappear.    How can I remove the watermark?


I got a problem. I got some coordinates in Excel. They are written with comma 14459091,1010 ex.  When I try to import them as csv-file into QGIS, it will only create a table and no points. When I look in the properties it says that my "x" and "y" columns are strings.  I use a semicolon to separate the fields.

i have read most of the related postings and answers allready ... (e.g.  and  ... among others)  but (!) unfortunately none of them solved my problem. as someone postet on 2012-01-04 12:27 definition of properly defined *.csvt doesn't effect field-import - they are expected to be numbers and still are string.  her is a sample of my csv  InputID,Mean,Stdev,min,max 1,334.7617168,36.87450474,294.4334857,383.5583136 2,446.3946568,207.949905,153.2494524,613.3182137 and the csvt "Integer","Real","Real","Real","Real"  .. i have already:    checked field names (no blanks), checked separators, ... which are qgis' default because the csv is distance matrix calculation result defined the csvt with simle "Integer","Real" and the precision-type-style "Integer(6)","Real(8.3)" changed country settings in win7, win8, osx 10.9 due to known decimal separator issues   used csv as specified as well as "excel-style" csv (";"-separated)    checked all that in qgis 2.0, 2.2, 2.3(master)   and: at the beginning this problem was related to distance matrix output  ... where qgis calculates the results (and writes the csv-outputs), which of course are numbers (mean, stdev, min, max)  so, initially i was just looking for a straight forward way to use qgis' own calculation results for mapping of distance-distribution ...  is there a way to solve or completely bypass the csv-t issue in a way, i can easily communicate to gis-beginners ?


We've recently noticed the following scenario happening in many of our databases:   A record is inserted, and receives an AUTO_INCREMENT primary key. The record is deleted. Another record is inserted, and receives the same AUTO_INCREMENT id as the deleted one.   I'm aware that this will happen for InnoDB tables (which is what these are) if MySQL restarts between setps 2 and 3, but it is not restarting. Is there any other event that will cause the AUTO_INCREMENT counter to be re-initialised? The time period between 2 and 3 can be a few minutes or up to a month.  Over the past month we've had some performance issues that we have so far resolved my increasing table_open_cache. The server has up to 8000 databases in use at any one time, and we found that we had a lot of processes in the "Opening tables" and "Closing tables" states. Could this be related?    Edit in response to Rick James' comment regarding FLUSH TABLES  The  (under "InnoDB AUTO_INCREMENT Counter Initialization") states that:     If you specify an AUTO_INCREMENT column for an InnoDB table, the table handle in the InnoDB data dictionary contains a special counter called the auto-increment counter that is used in assigning new values for the column. This counter is stored only in main memory, not on disk.    This is the counter that is initialised to MAX(id) + 1 on restart. However, the  states that:     This metadata is physically located in the InnoDB system tablespace.   This in turn links to the glossary entry for the system tablespace, which states that it is stored in "One or more data files (ibdata files)". This is contradictory but  I'm inclined to believe the InnoDB AUTO_INCREMENT documentation. If the counter were stored on disk in the system tablespace, there would be no need to initialise it with MAX(id) + 1.  If this is the case, then FLUSH TABLES would have no effect, but if the counter is persisted to the system tablespace then it should work. Does anybody know which part of the documentation is correct?

I need a way to keep auto-increment counter between mysql service restart.   As docs states by default after restart mysql autoincrement counter start from max(id)+1. How can I keep the last autoincrement value?  This is a big problem for me. I'm using envers to keep entities audits. I get as many errors as many "last rows" I delete.  Suppose I'm starting insert data into an empty table. Suppose to insert 10 rows. Then suppose to delete the last 8. In my table I will have as result 2 entities, with id 1 and 2 respectively. In the audit table I will have all 10 entities, with id from 1 to 10: entities with id from 3 to 10 will have 2 action: create action and delete action.  auto-increment counter is now setted to 11 in main table. Restarting mysql service auto-increment counter goes to 3. So if I insert a new entity, it will be saved with id 3. But in audit table there is already an entity with id = 3. That entity is already marked as created and deleted. It result in an assertion failure during update /delete action because envers cannot handle this inconsistent state.  Thanks


Which player has the most goals from free kicks in professional football history?

Who are the footballers with most free kicks scored? We all remember Juninho Pernambucano, but who else?


Okay, so I have dynamically generated images via PHP, so not necessarily the same images result. And I've spent the last four hours scanning the internet and trying countless things with jQuery and/or CSS, and I've come up with the following that works.                                        Market.png has a transparent background.  Now, the above works. On mouseover, it displays Market.png with the transparent background part being tile_4.jpg and out mouseout it is tile_4.jpg.  What I want to know: is there ANY way to accomplish the exact same thing as the above with jQuery or CSS? I haven't figured it out, and I've spent hours trying, but I'd rather do something else if at all possible since the above (with massive repetition, the above format is repeated currently around 100 times, but I have plans to expand it to over a 1000 times) will become a bandwidth hog.

I have a few images and their rollover images. Using jQuery, I want to show/hide the rollover image when the onmousemove/onmouseout event happen. All my image names follow the same pattern, like this:  Original Image: Image.gif Rollover Image: Imageover.gif  I want to insert and remove the "over" portion of image source in the onmouseover and onmouseout event, respectively. How can I do it using jQuery?


I use  which is built using .   It used to present me with notify-osd notifications on Ubuntu 15.10.  However, since the upgrade notifications look as follows:

I recently upgraded from Ubuntu 15.10 to 16.04. Every this is working fine but I am not getting slack notification properly. I am getting slack notification like alert box like shown in below picture.    Before this it appears upper right corner as shown in below picture.    Can any one help me to resolve this problem.?


How can I update my package l3kernel? I am presented with this error ! Package l3regex Error: Support package l3kernel too old. when I try to compile my document. Thanks

I'm trying to compile a document that only works with an up-to-date distribution, so I'd like to know: how do I update my distribution? Please provide screenshots where appropriate.  List of answers           To keep an eye on what’s going on at CTAN you may subscribe to the  or the RSS feed feed://www.mail-archive.com/ctan-ann@dante.de/maillist.xml


How this sentence "The weather being very bad, we did not start the journey" is reduced? I cannot understand what structure is applied for the clause "the weather being very bad".

Which is correct, and why?     some days we went on adventures — him maneuvering our scooter, me resting my chin …   or     some days we went on adventures — he maneuvering our scooter, I resting my chin …


How Stack Exchange related accounts are sorted by in user page.  Sorted by [rep], [badges] [answers]?  Also i have two other accounts with same [rep] my x account has more badges than the y account and the x account is showing after the y account, doesn't it matter on sorting if x account earned more badges than y?

How are accounts sorted if they have the same rep?    I don't see any logic.


A year ago, I changed my job and holding new 401K with my current Employer. I have not transferred my previous 401 K account to my new Employer.  I still maintain my existing 401 K account with my previous Employer. I haven't seen any Interest Rate growth in my previous 401K Account.  In this case, can i transfer my previous 401K account to my new 401 K Account and get some financial advise to diversify my portfolio ?

I recently started a new job and have a 401k from my previous employer that I don't know what to do with.  Should I roll it into my new employer's 401k, a traditional IRA or a Roth IRA?


I just voted to close . The question, on Stack Overflow, is simply about an Excel formula. I felt it belonged on , so I voted to close.  Is my logic there correct, or would Excel-fu be acceptable on Stack Overflow? (This is a fairly easy formula, if that matters any.)

Which Stack Exchange is the best site to ask questions about Microsoft Excel (as well as potentially other Microsoft Office and  questions)?


Blender's rendered useless as I can't access the toolbar and options menu. The cursor also selects things that are above it, for the example, on the side if I want to select the Camera, I'd have to click on the lamp.  I've tried running it in compatibility mode and playing with the window settings to a degree.  Any help would be greatly appreciated

I have a problem with Blenders UI. The "Info" bar on top disappeared and the mouse pointer is misaligned. I reinstalled Blender 2 times, deleted every leftover files  but it still does the same thing. This is in v2.78c. The weird thing is that on the bottom everything works fine. Here are some images:


Specifically, let's say I take a random sample of 20 products from a manufacturing batch of 1000 and they all tested good, what assumptions and conclusions can I make about the whole batch? Is it possible to say "There is an x% chance that the entire batch is good"? How could I calculate x in this case? Note that this is assuming I have no prior knowledge of what the defect rate should be.

I was wondering if there is a way to tell the probability of something failing (a product) if we have 100,000 products in the field for 1 year and with no failures? What is the probability that one of the next 10,000 products sold fail?


Suppose that $f$ is a twice differentiable real function such that $f''(x)>0$ for all $x\in[a,b]$. Find all numbers $c\in[a,b]$ at which the area between the graph $y=f(x)$, the tangent to the graph at $(c,f(c))$, and the lines $x=a$, $x=b$, attains its minimum value.  I understand that the area mentioned above is $$A(c)=\int\limits_a^b (f(x)-f(c)-f'(c)\cdot(x-c))dx,$$ and using this formula I can get that $c= \frac{a+b}{2}$ is a critical point of $A$, but I'm falling to see why this has to be where $A$ attains, specifically, a minimum. If anyone could enlighten me, that would be wonderful.

Consider the following problem:  Suppose that $f$ is a twice differentiable real function such that $f''(x)>0$ for all $x\in[a,b]$. Find all numbers $c\in[a,b]$ at which the area between the graph $y=f(x)$, the tangent to the graph at $(c,f(c))$, and the lines $x=a$, $x=b$, attains its minimum value.  The solution starts with the observation that the condition on $f''$ implies convexity of $f$, i.e. the graph of $f$ is always above any tangent to it, and therefore $$A(c)=\int\limits_a^b (f(x)-f(c)-f'(c)\cdot(x-c))dx,$$ where $A(c)$ is the area the problem refers. I'm really confused with this formula for the area and can't comprehend it even after drawing the picture. Can anybody explain it? Any help is appreciated.


I remember a friend of mine was trying to get me to implement this as a computer game. It came about around 2002-2006. Terrain pieces were stackable plastic hex pieces. Figures were similarly on hex pads, and had a series of stats. There were Ranged and melee attacks defined. Ranged attacks involved line of sight and measured distance from the tip of the weapon to a "vulnerable area" on the figure (shown in kind of a two color front and profile views on the associated chart). Characters had a mix of technology and magic (I remember one figure having a military rifle and a magic sword) and might have been drawn from different dimensions. There were some goblinoid characters also, I remember. And... that's most of what I remember at the moment, but it's bugging me.

I am trying to find a game that I had a starter set to when I was younger. I tried doing some online research, but honestly, I don't even know where to start and I can't find anything for it at my local comic/board game shop. I think that it was named something-"scape". I believe that I bought it sometime between 2003 and 2007, but my memory could be a little hazy on that that.  The Board  The board was different every time you played because it was made up of a bunch of chunks of hexagons (like honeycombs) that you could put together any way you want. You could even stack them on each other to create different levels. The hexa-combs were made out of plastic and I think they kinda clicked together.  Gameplay  Disclaimer: I was a kid when I played so I could have been disregarding any number of rules and not playing correctly at all, so take this with a grain of salt. You controlled a few different heroes and/or monsters (I remember a dragon that took up 2 spaces and I think an archer of some sort?). You moved around the terrain you built and did battle with the enemies heroes/mosters. I do not recall if it was a dice-based game or not. I think each character has a stats card. Unfortunately, I don't remember much about how it was actually played.  Expansion Sets  As I said, I think I had a starter set, which seemed to be generic-fantasy themed, but I think there were other sets that could be bought that had heroes/monsters from lots of other genres and more hexagons so that you could wind up with a huge battle with tons of genres mixing it up.  Can anyone point me to this game?


looking at df -h, I realized I have this /dev/loop0 mounted on /snap/core/3604 and it's always 100% full :   root@maxipc:~# df -h Filesystem      Size  Used Avail Use% Mounted on udev            7.8G     0  7.8G   0% /dev tmpfs           1.6G  9.9M  1.6G   1% /run /dev/sda3       116G   38G   73G  35% / tmpfs           7.8G   20M  7.8G   1% /dev/shm tmpfs           5.0M  4.0K  5.0M   1% /run/lock tmpfs           7.8G     0  7.8G   0% /sys/fs/cgroup /dev/loop0       84M   84M     0 100% /snap/core/3604 /dev/sda1       239M  111M  111M  50% /boot cgmfs           100K     0  100K   0% /run/cgmanager/fs tmpfs           1.6G   44K  1.6G   1% /run/user/1000   When I do a umount /snap/core/3604orumount /dev/loop0 it will unmount so it's apparently not busy at all(also when i try to remount /dev/loop0 again, it doesnt remount because, of course, it's not in fstab. in it, it looks like there is a whole little, cute and tiny root filesystem squashed in that 84M:   root@maxipc:~# ls -la /snap/core/3604 total 4 drwxr-xr-x 24 root root  333 Nov 30 12:39 . drwxr-xr-x  3 root root 4096 Dec 26 20:29 .. drwxr-xr-x  2 root root 1937 Nov 30 12:38 bin drwxr-xr-x  6 root root  129 Nov 30 12:38 boot drwxr-xr-x  4 root root 1160 Nov 30 12:38 dev drwxr-xr-x 80 root root 2399 Nov 30 12:38 etc drwxr-xr-x  2 root root    3 Apr 12  2016 home drwxr-xr-x 20 root root  406 Nov 30 12:38 lib drwxr-xr-x  2 root root   43 Nov 30 12:38 lib64 drwxr-xr-x  2 root root    3 Nov 30 12:35 media drwxr-xr-x  3 root root   45 Nov 30 12:39 meta drwxr-xr-x  2 root root    3 Nov 30 12:35 mnt drwxr-xr-x  2 root root    3 Nov 30 12:35 opt drwxr-xr-x  2 root root    3 Apr 12  2016 proc drwx------  2 root root   46 Nov 30 12:38 root drwxr-xr-x  8 root root  115 Nov 30 12:38 run drwxr-xr-x  2 root root 2349 Nov 30 12:38 sbin drwxr-xr-x  2 root root   58 Nov 30 12:39 snap drwxr-xr-x  2 root root    3 Nov 30 12:35 srv drwxr-xr-x  2 root root    3 Feb  5  2016 sys drwxrwxrwt  2 root root    3 Nov 30 12:37 tmp drwxr-xr-x 11 root root  151 Nov 30 12:38 usr drwxr-xr-x 12 root root  172 Nov 30 12:38 var drwxr-xr-x  2 root root    3 Nov 30 12:36 writable   and when I try to do a fuser -m /snap/core/3604 to see who uses the mount, nothing shows up. it reappears every single boot, and I don't know how the heck it's coming up, oh also, there is no sign of it in /etc/fstab. it's also squashfs file system. it looks like it's harmless but I just wanna know why it does what it does. what is it? any help/reply would be appreciated.  Thank you in advance,   MG  ps: I thought this question is different because the loop device is mounted as if it is an primary and working filesystem eventhough it's not busy at all. it gets umounted everytime if you want to, but it shows up again after boot. usually loop devices come up by df -H but for me this loop device comes up even among things that gnome graphical tools show, just like how a hardrive shows in your nautilus.

Recently I started learning more about snap packages and what intrigued me was that snap packages are mounted together with their own file system and dependencies (correct me if I'm wrong). Now, with all the great things that snaps bring to the table, what I'd like to know is:  Are snap packages always going to be mounted? This seems kind of awkward, since they appear in places like lsblk and give the impression of not being well integrated into my system.   Also, could they ever replace .deb and .rpm packages completely, or are they a different type of animal and are only complementary to .deb and.rpm packages?  As a side-note, I noticed that some applications are so self-contained that they don't respect any of my desktop settings like the mouse cursor theme or icon and menu themes.


Find the diameter of the new sphere assuming that the volume of  a sphere is proportional to the cube of its diameter. I know that diameter is equal to the twice of radius. How can you possibly solve this if the radius in the formula of the sphere is radius cube.

Three spheres of diameters 2,3&4 cm's respectively formed into a single sphere.Find the diameter of the new sphere assuming that the volume of  a sphere is proportional to the cube of its diameter


Prove that if $\{a,b,c\}$ forms a Pythagorean triple, then at least one of the three numbers must be divisible by $3$. Need some help with this one.

Show that if $x$, $y$, $z$ are integers such that $x^2 + y^2 = z^2$, then at least one of them is divisible by $2$, at least one is divisible by $3$, and at least one is divisible by $5$.  I know that $x,y,z$ are sides of a right-angled triangles. If I start putting values, then I can show, but have no clue about mathematical approach.  How do I solve it mathematically, using modular arithmetic?


I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps.  It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps?


Which of these sentences sounds correct?  These dynamics are used to explain the convergence toward an equilibrium state. These dynamics are used to explain the convergence towards an equilibrium state.  I have been reading a lot of posts, but I still have doubts. Need your suggestions :).

Which one should should I use? For some reason I have always used "towards", but I see some people saying "toward", like :     A great deal of his work in economic   theory has been directed toward   strengthening the foundations of our   understanding of central banking and   social insurance--indeed, one of my   most advanced macroeconomic classes   was nothing but a set of changes rung   upon a particular model that Peter   Diamond had advanced at...   Is there a difference between the two? When should they be used?


Today, I read a tweet where the used conditional structure did not fit any of the conditional types taught in the language books I've read.     if I would have relied on the Fake News of CNN, NBC, ABC, CBS, washpost or nytimes, I would have had ZERO chance winning WH [sic]   Basically, if I understand it well, it's structured as:     if (subject) would have (past participle) ..., (subject) would have (past participle)... .   I tried to search for conditional types and most sites listed Zero, Type 1, 2, 3 and mixed conditionals, but unfortunately, I didn't find any that resembles the quoted tweet.  Is 'if I would have ..., I would have ...' a valid/correct conditional?  If it is not, how bad it sounds to a native English speaker? How frequently is it used incorrectly?

I watched a (Hollywood?) film the other day where a character visiting his just-hospitalised wife (who it seems will actually survive) says "If I would have lost you [I don't know what I'd do]".  I'd always thought this was an error made by non-native speakers (I myself would only expect "If I had lost you"), but there was nothing to suggest that in the movie. Is it a regionalism?  EDIT: Actually, that wasn't true about only expecting "If I had lost you". I'd have been perfectly happy with "If I'd have lost you", so long as I didn't think too hard about what was being elided. I'd usually elide "have" there to just a schwa (neutral vowel) anyway, and think no more about it.


I think I must first prove that I(A) is a subring and then prove that A is in the ideal I(A) and I(A) is the largest sub-ring containing A. but I have problems to show that I(A) is a subring because let x and y in I(A), so $xa\in A$ and $ya \in A$  but I do not know how to prove that $xy\in I(A)$ and the rest.

Let $A$ be a ring and let $J$ be a right-sided ideal of $A$. We call the set $I_{A}(J)=\lbrace a \in A \mid aJ\subset J\rbrace$ the idealizer of $J$.  Show that $I_{A}(J)$ is the largest subring of that $A$ containing $J$ as an ideal.


ok, so I have a memory-based model to predict the values of variable X and I've also measured the real values of X. I have calculated both the RMSE and MAPE for the difference Xreal-Xpredicted. I know that there is absolutely no point in saying a model is good or bad if the RMSE value is less than a particular value. I was wondering though if there is a rule of thumb providing insights on the subject. For example my data range from 0 to 4 and I have an RMSE of 1,1. Is there any empirical rule suggesting this is a good/bad estimation?  thank you in advance   ETA: X may take all values within the range{-2,2}

I've fitted my model and am trying to understand whether it's any good. I've calculated the recommended metrics to assess it ($R^2$/ AUC / accuracy / prediction error / etc) but do not know how to interpret them. In short, how do I tell if my model is any good based on the metric? Is an $R^2$ of 0.6 (for example) sufficient to let me proceed to draw inferences or base scientific/business decisions?     This question is intentionally broad, to cover a wide variety of situations that members frequently encounter; such questions could be closed as duplicates of this one. Edits to broaden the scope beyond the metrics mentioned here are welcome, as are additional answers - particularly those that offer insight about other classes of metrics.


Select a tag e.g.  on MSE then click on the popular tab.  The description for feature-request is still displayed but the questions are no longer  questions.

After searching for and selecting a tag I am correctly redirected to the "New questions" tab (under questions) with filter: custom tags, the tag I selected in the filter field and its description underneath. Questions are also filtered by the selected tag. If I then navigate to the "popular" tab and select "hot" (which is default) no "filter" drop down exists, and questions are not filtered by the tag I have selected, however I can still see the tag description over the question list.  Steps to reproduce:   Click on a tag from your favorites tags on the right hand screen. Click on the popular tab.     Edit: Another aspect of this issue is that although when I am redirected to the "New questions" tab after a tag selection I get the questions filtered by custom tag, if I navigate to any of the other two tabs and then back to the "new" tab I no longer see the filtered questions and instead only see the selected tag's description. What is more, I don't even see the "filter" drop down in this case.  Steps to reproduce:   Select a tag from the favorite tags or from the tags page. The user is redirected to the "new" questions tab where questions are filtered by the selected tag as expected.  Click the "need answer" tab. The questions that need answer are displayed filtered by the selected tag. Go back to the "new" tab. The selected tag description is still there, however questions are no longer filtered and the "filter" drop down is no longer visible.


I have two random variables $X$ and $Y$ both being i.i.d. with a $U(0,1)$ distribution. I am trying to calculate the cumulative distribution function of $Z=X*Y$. Which would be the most efficient way to do this? Until now, I tried t put something together from here and try a similar approach:  However, I am really unsure if I can work similarly in my case. So this is my approach: $$ F_{Z}(z) = P(X*Y \leq z) = \int_0^1 P \left( Y \leq \frac{z}{x} \right)*\frac{1}{f_X(x)}dx $$ Is this approach still correct? Furthermore I am quite unsure how to continue from here, so any help is really appreciated.

Say $X_1, X_2, \ldots, X_n$ are independent and identically distributed uniform random variables on the interval $(0,1)$.  What is the product distribution of two of such random variables, e.g., $Z_2 = X_1 \cdot X_2$?  What if there are 3; $Z_3 = X_1 \cdot X_2 \cdot X_3$?  What if there are $n$ of such uniform variables? $Z_n = X_1 \cdot X_2 \cdot \ldots \cdot X_n$?


C# 6.0 adds this new ?. operator which now allows to invoke events like so:  someEvent?.Invoke(sender, args);   Now, from what I read, this operator guarantees that someEvent is evaluated once. Is it correct to use this kind of invocation instead of the classic pattern:  var copy = someEvent  if(copy != null)   copy(sender, args)   I'm aware of  where above version of pattern would require additional locks, but let's assume the simplest case.

Something that confuses me, but has never caused any problems... the recommended way to dispatch an event is as follows:  public event EventHandler SomeEvent; ... {     ....     if(SomeEvent!=null)SomeEvent(); }   In a multi-threaded environment, how does this code guarantee that another thread will not alter the invocation list of SomeEvent between the check for null and the invocation of the event?


So, I know this is a highly debated question... Okay so, can you use an Induction Motor to run two modified alternators at the same time, with one of them running the Electromagnets in the Induction motor and the other generating into something else. Will this create an excess of energy?   I know the name of this has already been asked but I'm wondering specifically about the above section.

I know this might sound stupid and maybe stupid totally, but I need some clarification....  I came through electric motor principle.  and then I came across the following link on DC generators    Now my question is, can't we combine them both to provide DC current with little DC used in motor side? By "combine," I mean using a DC generator coil only at the other side of the coil of the motor in the motor itself. The condition is that the 2 coils are connected via some apparatus that causes the 2nd coil to move along with the 1st coil.   In this way we can use both the mechanical energy produced by the 1st coil and the electrical energy produced by the 2nd coil, right?   This is a great concept if it works, right? Please throw some light on this.


Sometimes I'll start doing something fast. I've got something to do, and I need to get it done now.  Then of course i realize that I need to do something else to help me finish what I started, so I want to add a new shell using tmux (or screen)... but I forgot to start tmux right off....  My question is this:  How can I put a task to the background, start a tmux (or screen) session, and then resume my original task in tmux?

I have a running program on a SSH shell. I want to pause it and be able to unpause its execution when I come back.  One way I thought of doing that was to transfer its ownership to a screen shell, thus keeping it running in there.  Is there a different way to proceed?


I needed the field list related a vocabulary item.I was able to list the fields related to a content type by using like this: \Drupal::entityManager()->getFieldDefinitions('node', 'article');  But I can't find a way for the vocabulary items.

In Drupal 7, to get all fields used in a content type, I use the following code. $fields = field_info_instances('node', 'article');  What is the equivalent for Drupal 8?


Suppose we want to compute the covariance between $z_1$ and $z_2$ given as follows: $$ z_1 = a_1 \cdot x_1 + a_2\cdot x_2 \\ z_2 = a_3 \cdot x_1 + a_4 \cdot x_2\\ % x_1,x_2 \sim p(x) $$ If we compute the covariance between $z_1$ and $z_2$  we have: $$ \mathbb{E}[z_1\cdot z_2] - \mathbb{E}[z_1]\cdot \mathbb{E}[z_2]   = \\ \mathbb{E}[a_1a_3 x_1x_1 + a_1a_4 x_1x_2 + a_2a_3 x_1x_2 + a_2a_4 x_2x_2] - a_1a_3\mathbb{E}[x_1]^2 -a_1a_4\mathbb{E}[x_1]\mathbb{E}[x_2] -a_3a_2\mathbb{E}[x_1]\mathbb{E}[x_2] -a_2a_4\mathbb{E}[x_2]^2 =\\ a_1a_3\text{cov}[x] -a_2a_4 \text{cov}[x] $$ In what I am studying, the last equality holds (or at least that is what I have understood), from the fact that $x_1$ and $x_2$ are independent hence their covariances is zero.

Let $A$ and $B$ be two constant matrices and let $x$ and $ y$ be two random vectors, what is the general formula for $Var(Ax+By)$? I know the formula for when $x$ and $y$ are scalar random variables and $A$ and $B$ are constants, but what about the matrix case?


I see that without this last requirement $n^r(X_n-X)$ would blow up in probability, how to prove this formally? By contradiction maybe? Like assuming it doesn't converge in probability and hence finding a subsequence such that $\mathbb{P}(|X_n-X|>\varepsilon)>\Delta$ for all $k$, and then showing that this implies $n^r(X_n-X)$ to go to infinity in probability?

Question: If $n^r(X_n-X)$ converges in distribution for some $r>0$, do we have that $X_n$ converges to $X$ in probability?    As $P(n^r|X_n-X|>\varepsilon)\to P(|Z|>\varepsilon)$ (where $Z$ is the random variable to which $n^r(X_n-X)$ converges), can we say something about $P(|X_n-X|>\varepsilon)$?


I'm trying to compile a Feynman technique-esque definition for pertinent physical concepts. Here is mine for what I understand of angular momentum, in particular, conservation of angular momentum     Conservation of Angular Momentum      Basically, it means the energy from changes of angular momentum is   conserved. If an ice skater moves her arms to her chest, she gains   energy from the system of her rotation. That sentence sounds bizarre   but bare with me. When she's spinning with her arms out, her arms feel   an inward force that keep her arms from falling off her body tangent   to the path of motion. When she moves along that direction when   pulling in her arms, that inward force is now doing work on her. The   work done is giving her kinetic energy, which amounts to an increase   in the speed in her arms, and thus a higher angular velocity. When she   brings her arms from close to her body to away, she is now doing   negative work from the same basic concept from before, but this work   is now going to be due to her, so she transfers energy into the   system of her rotation. As long as no external force from her body,   say chemical energy, arises, and her moving is a constant velocity,   the energy between these states are conserved.   Okay, so I don't like the sentences "If an ice skater her arms to her chest, she gains energy from the system of her rotation." and "So she transfers energy into the system of her rotation." If what I'm saying is true, what exactly is this "system of rotation" I'm trying to describe? When her arms go outward again, and her speed decreases, she clearly transferred energy, but to where, exactly?

The following quote comes from:      Consider an ice skater that has just gone into a spin with arms   stretched out.  If it helps, the skater is wearing lead bracelets on   each wrist.  As the skater spins, the angular momentum and angular   kinetic energy are constant;  friction with the air and with the ice   can be eliminated.  The skater must exert an inward centripetal force   on the bracelets to keep them rotating in the same circle, but this   force does no work, since the bracelets are not changing their radius   of rotation.      Then the skater pulls in his arms and the bracelets, closer to his   axis of rotation.      Several interrelated things happen:           since there is no external torque, the angular momentum of the system stays the same;   Since the various masses of the skater are all moving towards the axis of rotation, the total moment of inertia of the system   decreases;     Combining 1 and 2, the angular velocity of the system increases;  if the moment is halved, the angular velocity doubles   Combining 2 and 3, with some quantitative treatment, the angular kinetic energy increases;  if the moment is halved and the   angular velocity is doubled, the kinetic energy doubles;   The skater does work;  his arms are now exerting an inward force through a distance as his arms draw the bracelets inward;  the work done can be rigorously shown to be identical to the increase in   kinetic energy...      However, it only covers a case when work is done to pull arms inwards. It is understandable that the work would be done in such case.  But what is happening in the opposite case when the skater has their arms inwards and lets them go outwards? S/he doesn't do any work but kinetic energy (and total energy) is lost. Why is it lost?  E.g.  I = 2kg * (1m)^2 w = 3.14/s L = 2kg * m^2 * 3.14/s Ek = 9.869  After shifting 2kg by 0.1m outwards: I = 2kg * (1.1m)^2 = 2.42 kg * m^2 L = 2 * 3.14 = 2.42 * w w = 2.5963 Ek = 8.1566   So, where did 1.7124 J go?  The quoted answer describes the easy case and omits the hard one.


I have a host OS running Windows 7 and guest OS running Ubuntu on Virtualbox.  What if I want to "install" my image of Ubuntu virtual machine as ordinary Ubuntu installation. Is it possible and how?

Is is possible to convert a .vdi file into a .iso that can be burned to a cd or dvd and make it like an installer. Or Is it possible to convert virtual machines to physical environments?


I have an image that I want to rotate in compositor, to mix it with another image later. But as you can see in the images attached, when I use the rotate node, the image gets cropped.  I could create a plane in 3DView and render it, but I would prefer a shorter solution inside the compositor.  Is there any way to extend the canvas of the image, so this operation can be done?

As you can see, if I try to translate an image in the compositor, it does not affect the actual bounds of the image, only the pixels themselves.       The same thing happens when trying to scale an image:    So the image cannot be moved or scaled further than the actual dimensions of the image without clipping it.  The render border size does not seem to affect it: (Seen here with a gradient texture to define where the render dimensions are.)    For some reason skipping the blur node makes it work, but with it it gets cropped.  Aside from creating a lot of transparent space around the image in an external image editor or scaling the Pixels down with a Scale node, How can I accomplish this?


Is there a clean/best way to set a variable inside a object only if its unassigned or null ? Example: currently I am doing this. if (item.getLocation() != null) {     item.setLocation("/somelocation"); }

I use object != null a lot to avoid . What is an alternative to: if (someobject != null) {     someobject.doCalc(); }


I have seen many times that sometimes when I downvote a post , my repuation decrements by -1 and sometimes it does not?  What is the reason behind it?   And what are the exact scenarios when this happens?

On Stack Exchange, users may gain a certain level of reputation.  What does reputation do? How can a user gain or lose reputation?   See also   in the Help Center  - Maximum amount of votes a user can use in a day and reputation requirements to vote.  - How to get an exact overview of the actions that got you your reputation.  - A full list of all privileges granted at each reputation level on all sites.


I’m writing my thesis and I submitted a paper on the same topic to a conference, where it got accepted. However, the contents such as methods, results, and conclusion are identical in text, i.e. I copy pasted the content from thesis to the paper.  Now I want to submit my thesis but I suppose it is self-plagiarism if I don't cite my paper. My question is, can use the same content in my thesis and paper if yes then how do I mention that content is reused? or should I rephrase my complete thesis now and then cite paper? But if I rephrase then how about the experiment results and figures? should I cite paper there as well?

I have finished my master thesis and now a couple of colleagues who were involved (one of which was the supervisor) are interested in "extracting a paper" from it. We have already written one paper on a topic covered in the thesis, but in a bit more detail. I am worried that this would be considered self-plagiarism since I have already done the thesis and am only really summarizing one part of the thesis.


Is gravitational attraction increased by relativistic mass as well as rest mass?   If so what would happen if an observer travelled at relativistic speeds? Would it appear to him that the whole universe had acquired a greater mass as it was moving at relativistic speed towards or away from him and hence start accelerating towards him under greater gravitational attraction?   Similarly would it mean that the universe was suddenly hugely more energetic that it was before with much higher balancing gravitational potential?

I'm a big fan of the podcast Astronomy Cast and a while back I was listening to a Q&A episode they did. A listener sent in a question that I found fascinating and have been wondering about ever since.   From the show :      Arunus Gidgowdusk from Lithuania asks: "If you took a one kilogram mass and accelerated it close to the speed of light would it form into a black hole? Would it stay a black hole if you then decreased the speed?"   Dr. Gay, an astrophysicist and one of the hosts, explained that she'd asked a number of her colleagues and that none of them could provide a satisfactory answer. I asked her more recently on Facebook if anyone had come forward with one and she said they had not.  So I thought maybe this would be a good place to ask.


Could anyone explain the difference between the below commands:  su - oracle   and   pbrun /bin/su - oracle

What is difference between pbrun and sudo command? I have seen people executing pbrun sudo su - what this means?  I know su -, it will try to switch to root user. What speciality pbrun gives to sudo when it is used along with sudo command?


I am using Lubuntu and was trying to install Porteus to pendrive. But I accidentally installed it to hard disk where I was using bodhi linux.  Now I use Lubuntu from second partition and it is good to use. I want to remove bodhi linux from first partition without loosing data.  I tried to copy data from that partition but in last it says can't copy data permission denied read only file system   I think I need to boot in bodhi linux for that data but I am unable to boot in.  Someone please help me to remove bodhi linux from the first partition without loosing data.

I have latest ubuntu 15.4. I wanted to try fedora so I installed it afterwards and got dual boot. Now I want to remove fedora and stay with only ubuntu.   How do I completely remove fedora and retrieve the space I gave it ? How do I remove grub ?   please write in details. I saw  but it has little details and I counldn't manage to do that.    update: I tryed what kyodake suggested and still don't understand how to merge the 2 partitions. Bellow is the current status in my gparted: (I want to merge sda4 (deleted fedora) to sda1 (my ubuntu)). How do I mount it exactly ?


Here is the PDF I will referring to.:    The algorithm I'm referring to (which can also be found in the PDF file, above) is the following.:  public static long fibonacciBad(int n) {     if(n <= 1)         return n;     else         return fibonacciBad(n-2) + fibonacciBad(n-1); }   I'm trying to understand why fibonacciBad is O( 2^(n/2) ), assuming that I'm correct in that being what the PDF is implying.   I suspect that it has to do with using B for every second numbers of calls in A, but the specifics are unclear to me. Also, could someone please give me an intuitive explanation as to why it's okay for it to be every second number of calls in order to be considered exponential (instead of every single number of calls being at least double the previous one)? (I'm making up this alphabetical notation, A and B, for below. This notation isn't used in the PDF linked to here.)  A:  c_0 = 1  c_1 = 1  c_2 = 1 + c_0 + c_1 = 1 + 1 + 1 = 3  c_3 = 1 + c_1 + c_2 = 1+ 1 + 3 = 5  c_4 = 1 + c_2 + c_3 = 1 + 3 + 5 = 9  c_5 = 1 + c_3 + c_4 = 1 + 5 + 9 = 15  c_6 = 1 + c_4 + c_5 = 1 + 9 + 15 = 25  c_7 = 1+ c_5 + c_6 = 1 + 15 + 25 = 41  c_8 = 1 + c_6 + c_7 = 1 + 25 + 41 = 67   B:  1 + 2 + 4 + ... + 2^(n-1) = 2^n - 1

I understand Big-O notation, but I don't know how to calculate it for many functions. In particular, I've been trying to figure out the computational complexity of the naive version of the Fibonacci sequence:  int Fibonacci(int n) {     if (n <= 1)         return n;     else         return Fibonacci(n - 1) + Fibonacci(n - 2); }   What is the computational complexity of the Fibonacci sequence and how is it calculated?


I'd like to create a virtual machine of an old laptop and then get rid of the old laptop.  How does licensing of Microsoft xp operating system work?  The operating system was pre-installed on the laptop from the manufacturer.  Can I license with the sticker on the laptop?

We get a lot of questions on Super User about Windows activation and licensing. This question is an attempt to answer the most common questions in one place with a .   When reinstalling Windows, the following questions often come up:   Can I transfer the copy of Windows from my old computer to a new one? Does the license key on the sticker on my computer work on any computer? If I have a 32-bit version, can I install a 64-bit version? I have an OEM version of Windows, but only a retail disk. Can I still use it? I want to install Windows with a different language. Do I need a new license in that language? I changed some hardware. Will I be able to reactivate my computer? Can I back up my activation before doing a reinstall? How many computers can I install my license on? Do I have to deactivate my old installation before transferring a license? If so, how? How does licensing work in Windows ? What are the restrictions on transferring, reinstalling, and changing versions of Windows?


The problem states:     Let $\Bbb R$ denote the set of all real numbers. Find all functions $f : \Bbb R \rightarrow \Bbb R$ such that $$f(x^{2}+f(y))=y+(f(x))^{2} \space \space \space \forall x, y \in \Bbb R.$$   My progress: 1. If we substitute $x=y=0$ in the given equation, then we get $$f(f(0))=(f(0))^{2}.$$ 2. We then substitute $x=0$ in the given equation and find out that $\forall y \in \Bbb R$, $$f(f(y))=y+(f(0))^{2}.$$ 3. Now, we observe that, for all $x,y \in \Bbb R$, $$y+(f(x))^{2}=f(x^{2}+f(y))=f((-x)^{2}+f(y))=y+(f(-x))^{2}.$$ Hence $\forall x \in \Bbb R,$ $$f(-x)=f(x) \space \space or \space \space f(-x)=-f(x).$$ 4. But, if for some $x \in \Bbb R$, $f(-x)=f(x)$, then we would have, $$x+(f(y))^{2}=f(y^{2}+f(x))=f(y^{2}+f(-x))=-x+(f(y))^{2}$$ for any $y \in \Bbb R$ implying $x=0$. So, for any $x \neq 0$, $f(-x)=-f(x).$ 5. Now if there exists any $y \neq 0$ such that $f(y) \neq 0$ then, $$y+(f(0))^{2}=f(f(y))=f(-f(-y))=-f(f(-y))=y-(f(0))^{2}$$ which implies $f(0)=0$. So, if $f(0) \neq 0$, then $f(x)=0$ whenever $x \neq 0$. But then $f(0) \neq 0$ would imply $(f(0))^{2}=f(f(0))=0$ which cannot happen and hence $f(0)=0$. 6. So summing up all that we have got so far, we see that $f$ has the following properties:   (i)$f$ is an odd function.(ii)$f(x^{2})=(f(x))^{2}.$ (iii)$f(f(x))=x.$  This is where I am stuck. I have observed that using the above mentioned three properties, we can write the given equation as $$f(x^{2}+f(y))=f(x^{2})+f(f(y))$$ which is almost $f(a+b)=f(a)+f(b)$, but that is of no help. Any hints would be welcome.

Let $\mathbb R$ denote the set of all real numbers. Find all function $f: R\to \ R$ such that   $$f\left(x^2+f(y)\right)=y+(f(x))^2$$   It is the problem. I tried to it by putting many at the place of $x$ and $y$ but I can't proceed. Please somebody help me.


On a fresh install of windows 10 (final build), my "search windows" is broken..  It won't find any of my apps when I search. E.g. "sublime" for sublime text, "internet" for IE, nothing. WHen I click "search my stuff" and filter to "apps", I get a "Something went wrong".  I've turned Cortana off, and web results. I've rebuilt my search index, and changed the locations to make sure it's searching in places I know the start menu to be... I've also run the windows troubleshooter, with no joy.

For the past several versions (since Windows Vista, I think), if you hit the Windows key and start typing, Windows will search for applications.  Since upgrading to Windows 10 with , she is only hit or miss at finding applications. And she doesn't do partial searches, either.  Some examples:   WinKey + type "Paint" does not find "mspaint". Instead it suggests some applications from the store. WinKey + type "Excel" does not find Excel. Nor does typing "Word" find Word. However, typing OneNote finds OneNote.   What is the reason for this behavior and how I can get Cortana to find the applications installed on my machine again? Is there a setting I am missing?    If I browse to "C:\ProgramData\Microsoft\Windows\Start Menu\Programs" I can see that the shortcuts for these applications all still exist. But Cortana is not finding them. Everything from the Microsoft Office applications to  to  to hundreds of other applications I have installed.  Where can I set which folders Cortana indexes?    As you can see in the screen shot below, this Start Menu folder is, indeed, indexed:    However, none of these applications are coming back as search results from the "start" menu.  It may be related to  as well.  I did a brand new install of Skype (for desktop), and it shows up nowhere in the start menu. And typing in "Skype" to search for the application does not find it. But the shortcut to Skype is definitely in this location:  C:\Users\Patrick\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Skype     EDIT  The latest Windows 10 update (Threshold 2) has solved this issue for me. Cortana now finds all my files with no issues. Previously my only solution was to use , I've been able to uninstall that now and use the standard Windows Start menu.


Did you know Australia was home to megafauna 40-50,000 years ago? They were huge! Our , which is very appropriately named, was a wombat that stood taller than an adult. So too did our largest kangaroo, the . If these facts are terrifying to you, it's okay. They went extinct around the time humans arrived here, so they have your back. So does the chat onebox mechanism, which will handily erase all terrifying facts.  But really, the chat probably shouldn't do that. They are extinct, and we can handle it.

Random text is getting dropped from Wikipedia oneboxes. See . Screenshot:  This occurs regardless of HTTP/HTTPS and of whether a redirect URL is entered into chat. I initially thought the bug is triggered by <span>s or other HTML formatting elements, but in the Burj Khalifa article's HTML source code, there is no formatting around one of the deleted words. Possibly related to , but this is not specific to numbers.


I have a Stored Procedure with the hint WITH RECOMPILE, so the Stored Procedure do not store in the cache a Query Plan for the Stored Procedure. The average time the Stored Procedure resolve the Query is between 1 and 3 second, but from time to time the Stored Procedures takes > 30 seconds and sometimes it gets timeout. The strange thing here is that I run DBCC FLUSHPROCINDB and the Stored Procedure returns to its normal time (1 to 3 seconds).  Do you have any idea of what could be happening?

Background  I have a query running against SQL Server 2008 R2 that joins and/or left-joins about 12 different "tables". The database is fairly large with many tables over 50 million rows and about 300 different tables. It's for a large-ish company that has 10 warehouses across the country. All the warehouses read and write to the database. So it's pretty large and pretty busy.  The query I'm having trouble with looks something like this:  select t1.something, t2.something, etc. from Table1 t1     inner join Table2 t2 on t1.id = t2.t1id     left outer join (select * from table 3) t3 on t3.t1id = t1.t1id     [etc]... where t1.something = 123   Notice that one of the joins is on a non-correlated sub-query.  The problem is that starting this morning, without any changes (that I or anybody on my team knows of) to the system, the query which usually takes about 2 mins to run, started taking an hour and a half to run -- when it ran at all. The rest of the database is humming along just fine. I've taken this query out of the sproc that it usually runs in and I've run it in SSMS w/ hard-coded parameter variables with the same slowness.  The strangeness is that when I take the non-correlated sub-query and throw it into a temp table, and then use that instead of the sub-query, the query runs fine. Also (and this is the strangest to me) if I add this piece of code to the end of the query, the query runs great:  and t.name like '%'   I've concluded (perhaps incorrectly) from these little experiments that the reason for the slow-down is due to how SQL's cached execution plan is set up -- when the query is a little different, it has to create a new execution plan.  My question is this: When a query that used to run fast suddenly starts running slowly in the middle of the night and nothing else is affected except for this one query, how do I troubleshoot it and how do I keep it from happening in the future? How do I know what SQL is doing internally to make it so slow (if the bad query ran, I could get its execution plan but it won't run -- maybe the expected execution plan would give me something?)? If this issue is with the execution plan, how do I keep SQL from thinking that really crappy execution plans are a good idea?   Also, this is not a problem with parameter sniffing. I've seen that before, and this is not it, since even when I hard-code the varaibles in SSMS, I still get slow performance.


In my Windows 7 Ultimate 64-bit, I was deleting unused usernames in Advanced Profile management window (I could not remember the exact name but there were three buttons: Add, Remove, Properties) which others have created temporarily.   Since I was using shortcut key for Remove button I didn't stop pressing the shortcut key while my username also came to selection and got deleted, furthermore I pressed the OK button for the confirmation dialog box. So tried to recover in the hope of it will be recovered, I create the username account with same username by Computer->Right Click->Manage->Local Users and Groups->Users.  When I restart I realized I no longer have administrator rights. So whenever I try to do administrator things (My password accepts on login, but not when I try to change password in control panel) it asks username and password with administrator privilege.  I am using Dell GX620 PC. I've disabled DVD/USB for standard users. So now I even not able to insert DVD to reinstall the OS.  So How can I retrieve my username or format the OS in this situation?

I accidentally disabled my admin account.  After I login to another account I found I can not get admin rights, because all admin accounts on my computer are disabled.  I clicked on 'run as administrator' but only see a smart card choice (all the admin accounts are disabled so no choice provided)    I don't want to re-install my OS, help!    Details:  I have account A on my computer.    I got a new computer so I want to give the old one to my mother.    Creating a new user account B for her and disable account A.    Logout and restart.    Successfully login B, now I found I could not get admin rights because no account choice is provided.    More informations about my machine:  OS is Windows 10 and my admin account is a Microsoft Account.  I have an arch-linux installed on my computer and dual-boot it using GRUB, so maybe I can not use safe mode.


I have a transfer in Frankfurt. I will have five hours between flights. Will that be enough to visit the city center? And what should I use to get to the city center?

Is layover time of 5 hours and 25 minutes enough to visit Frankfurt ?   Both flights are international with Lufthansa and on one ticket, so I will have the boarding pass of the second flight with me. Will arrive and departure to/from terminal 1 and do not need visa to enter Germany.


I am developing a python addin that allows the user to click on a location in arcmap and a browser window opens with the associated area in google maps.   The issue I am currently facing is that the formula I use creates a discrete zoom level resulting in zoom levels with 10 decimals, such as 17.7875321547z or 18.9062909847z.   The Formula I am using:  level = (36.906 * scale**-0.088)  url = "https://www.google.com/maps/@{0},{1},{2}z".format(y_coord, x_coord, level)  My issue is that the url shows my provided zoom level but then rounds it down to the nearest whole number. From 17.7875321547z to 17 and so on.   I have found a similar question () that was asked almost 3 years ago with the only answer being that google had not fixed the issue at that point.   Has there been any progress since then?   Is there a way to use the specified zoom level without google rounding it?

I'm not sure if this is new in the Google maps site but you can use the scroll bar to zoom in-between the standard zoom levels.  The plus and minus buttons still jump a full zoom level and there doesn't appear to be any change in the raster in the in-between zoom levels although some road labels change (are they vector then?)  Can I get a static map at the in between zoom level as I often want it a bit more zoomed in but not all the way to the next level?  Also is the in-between zoom available in the JavaScript API?   It doesn't look like this is possible from the Google documentation but that's not always very up to date.


I am trying to prove that if $R$ is a PID and $P$ is a prime ideal of $R$ then $R/P$ is also a PID. This is question 8.2.3 from Dummit & Foote.  My thoughts and what I know : $P$ is also maximal. $R/P$ is hence a field. Also is an integral domain due $P$ being prime. $P$ is generated by by some element of $R$, say $a$, written as $P=(a)$. My conjecture is that an ideal $I$ of $R/P$ is generated by the coset $a+P$, ie. $I=(a+P)$.   I am having some trouble understanding that the set $I$ is equal to a set generated by a coset. I'm not sure how to show the inclusions to show that those two sets are the same. Any help is appreciated. Thanks for your time.

Please help me prove that      the quotient of a principal ideal domain by a prime ideal is again a principal ideal domain.   This was from Abstract Algebra


I am trying to use Javascript to shrink and grow automatically as the height of the scroll is increasing. The growing the height of textarea is achieved but when I am deleting the texts I can't figure out how to shrink the size.... I don't want to use the jQuery functions. My code is: <html> <head>   <script>     function func() {     var ta = document.getElementById('mytexta');     ta.value+=ta.scrollHeight+' '+ta.clientHeight;     if(ta.scrollHeight>ta.clientHeight)       {         ta.style.overflow='hidden';         ta.rows+=1;       }                      }   </script> </head> <body>    <textarea class="mytext" onkeyup="func()" id="mytexta" style="overflow:hidden;">Here we go</textarea>   </body>   </html>

There was , which I've tried. But there is one problem: the textarea doesn't shrink if you delete the content. I can't find any way to shrink it to the correct size - the clientHeight value comes back as the full size of the textarea, not its contents.  The code from that page is below:  function FitToContent(id, maxHeight) {    var text = id && id.style ? id : document.getElementById(id);    if ( !text )       return;     var adjustedHeight = text.clientHeight;    if ( !maxHeight || maxHeight > adjustedHeight )    {       adjustedHeight = Math.max(text.scrollHeight, adjustedHeight);       if ( maxHeight )          adjustedHeight = Math.min(maxHeight, adjustedHeight);       if ( adjustedHeight > text.clientHeight )          text.style.height = adjustedHeight + "px";    } }  window.onload = function() {     document.getElementById("ta").onkeyup = function() {       FitToContent( this, 500 )     }; }


My aim is to include a local geojson file in my Leaflet map application using  , as suggested by  earlier answer. In my root directory, I have:  index.html entire contents of  leaflet.ajax.min.js containing the contents of the source file on  bb4326.geojson containing 4 point features in EPSG4326  Index.html looks like: <!DOCTYPE html>       <title>Hey up here!</title>     <meta charset="utf-8" />     <meta name="viewport" content="width=device-width, initial-scale=1.0">     <link rel="shortcut icon" type="image/x-icon" href="docs/images/favicon.ico" />     <link rel="stylesheet" href="https://unpkg.com/leaflet@1.7.1/dist/leaflet.css" integrity="sha512-xodZBNTC5n17Xt2atTPuE1HxjVMSvLVW9ocqUKLsCC5CXdbqCmblAshOMAS6/keqq/sMZMZ19scR4PsZChSR7A==" crossorigin=""/>

     Opening index.html in a browser results in the basemap at the requested location and zoom-level, but the geojson file contents are not displayed. What am I overlooking? I thought that the ajax.min.js script ought to load the dataset for me? bb4326.geojson was created by exporting a Shapefile to GeoJSON in QGIS and looks like: { "type": "FeatureCollection", "name": "bb4326", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } }, "features": [ { "type": "Feature", "properties": { "id": 1, "cat": "A" }, "geometry": { "type": "Point", "coordinates": [ -1.903211081088789, 52.483536707820782 ] } }, { "type": "Feature", "properties": { "id": 2, "cat": "A" }, "geometry": { "type": "Point", "coordinates": [ -1.569431757803851, 55.041100936161001 ] } }, { "type": "Feature", "properties": { "id": 3, "cat": "B" }, "geometry": { "type": "Point", "coordinates": [ -0.164490580870734, 51.446934150191545 ] } }, { "type": "Feature", "properties": { "id": 4, "cat": "C" }, "geometry": { "type": "Point", "coordinates": [ -3.239562634800648, 51.514642158718445 ] } } ] }

I'm a beginner in Leaflet and I need help to deal with GeoJSON files.  I succeeded in creating a Leaflet basemap. I can add markers without troubles but I cannot manage to show a GeoJSON layer.  Here is the code I picked up from Leaflet Tutorials website  :  var geojsonFeature = {     "type": "Feature",     "properties": {         "name": "Coors Field",         "amenity": "Baseball Stadium",         "popupContent": "This is where the Rockies play!"     },     "geometry": {         "type": "Point",         "coordinates": [-104.99404, 39.75621]     } }; L.geoJSON(geojsonFeature).addTo(map);   Unfortunatly, the GeoJSON does not appear in my map.   Can you tell me where I missed something ?    Alright, you're fine Francisco, this part was OK. I changed the whole script and it works !  However, would you know how to load a GeoJSON from an external source ?  I tried this :   var geojsonLayer = new L.GeoJSON.AJAX("foo.geojson");        geojsonLayer.addTo(map);   from   but this definitely does not work.  Any ideas ?    I am not skilled enough to understand your advice.  Here is the whole code I am using to create my map :  <!DOCTYPE html>   <title>data</title> <meta charset="UTF-8"> <link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.3/dist/leaflet.css" />

      I know it's a bit messy but this is actually my very first HTML script... I guess I did not include in a proper way the AJAX library.    Actually, I just want a solution to replace the lines where I create the GeoJSON by something that tells javascript to load the GeoJSON stored locally in my folder. This :  var geojsonFeature = {     "type": "Feature",     "properties": {         "name": "Coors Field",         "amenity": "Baseball Stadium",         "popupContent": "This is where the Rockies play!"     },     "geometry": {         "type": "Point",         "coordinates": [-104.99404, 39.75621]     } };   should be transformed into something like (I don't know if it exists) :  var geojsonFeature = [foo.geosjon]   where "foo.geosjson" is a file like :  { "type": "FeatureCollection", "name": "abies", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } }, "features": [ { "type": "Feature"


I want to draw figures on different planes in TikZ. Consider an example of drawing a simple rectangle in the xy plane at z=0 and another rectangle in the xy plane at z=2. Generally, the planes I am considering will also include some rotations (see below for details) in addition to displacements from the origin O. I have seen this  which uses different canvases, but I'm not sure how to adapt that.   I am looking to use the scope environment that allows me to displace a plane and rotate it. That way any figures drawn within that scope appears within that plane.  Detail on the rotations considered here The rotations referred to here are along the axes x,y,z. For example, consider I have two planes: one that has the origin O = (0,0,0) at the bottom left corner and a second plane that has the origin at O' = (2,0,0). Rotations of plane 2 are along the axes that intersect the point O.  Here is a MWE that sets up the basic problem:  \documentclass{standalone}  \usepackage{tikz}  \usepackage{tikz-3dplot}  \usetikzlibrary{arrows.meta}  \begin{document}  \tdplotsetmaincoords{60}{130}  \begin{tikzpicture}[scale=2,tdplot_main_coords]  \draw[thick,->] (0,0,0) -- (5,0,0) node[right]{$x$};  \draw[thick,->] (0,0,0) -- (0,5,0) node[above]{$y$};  \draw[thick,->] (0,0,0) -- (0,0,5) node[below left]{$z$};  %Circle in xy plane at z=0  \filldraw[fill=blue!40!white, draw=black] (0,0,0) rectangle (4,4,0);  %Another circle at xy plane at z=2  %\filldraw[fill=blue!40!white, draw=black] (0,0) rectangle (4,4);  \end{tikzpicture}  \end{document}

Overview  So say I want an arc between the x and z axis in the same way the following creates an arc between the x and y axis (MVCE):  \documentclass[border=5mm]{standalone} \usepackage{tikz} \begin{document}   \begin{tikzpicture}     \tikzset{       x={(0:1cm)},y={(50:0.7cm)},z={(90:1cm)}     }     \draw[->] (0,0,0) --++ (1,0,0) node[right]{$x$};     \draw[->] (0,0,0) --++ (0,1,0) node[right]{$y$};     \draw[->] (0,0,0) --++ (0,0,1) node[right]{$z$};     \draw (0,0,0) ++(0:.3) arc (0:90:.3);   \end{tikzpicture} \end{document}     One solution to this exact problem is to do scope and tell arc that the y-axis is the z-axis.      \begin{scope}       \tikzset{y=(90:1cm)}       \draw (0,0,0) ++(0:.3) arc (0:90:.3);     \end{scope}   The problem  However, I need this more generic since I don't necessarily know how the y-axis is defined, so I'm looking for a way to do, essentially this:      \begin{scope}       \switchYZAxes       \draw (0,0,0) ++(0:.3) arc (0:90:.3);     \end{scope}   or      \begin{scope}       \tikzset{y=\theZAxis}       \draw (0,0,0) ++(0:.3) arc (0:90:.3);     \end{scope}   The latter is problematic because it seems like I can't send polar coordinates to the \tikszet via a macro (which is the background for  question).  Any ideas? Thanks :)


I've HTC DESIRE 326g dual SIM with kit Kat working fine. I want to place a shortcut or any file actually on home screen . How to do that . Thanx in advance.

I have a text file somewhere on the SD card.  How can I create a shortcut to this file on the "desktop" to open it immediately?  (HTC Wildfire)


I'm on SQL Server 2014 and I have a User table:  +----+------+-----+ | ID | Name | ... | +----+------+-----+ | 11 | John | ... | | 12 | Jack | ... | | .. | .... | ... | +----+------+-----+   And I have many tables which references this one. Can I get a list of all tables which references this table? And, in particular, can I get a list of all tables which references a particular row on this table?  I will then need to update all references to User 12 to User 11.

I want a way to establish which columns in a given database are joined via PK/FK relationships. I can return the PK/FK information for a given table via   SELECT *   FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS cu  WHERE EXISTS (     SELECT tc.*      FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc      WHERE tc.CONSTRAINT_CATALOG = 'MyDatabase'           AND tc.TABLE_NAME = 'MyTable'           /*AND tc.CONSTRAINT_TYPE = 'PRIMARY KEY'*/         AND tc.CONSTRAINT_NAME = cu.CONSTRAINT_NAME); GO   but for a PK returned from such a query how do I establish the associated FK (assuming there is one)?  I know you can also get the referenced tables via:  SELECT CONSTRAINT_NAME = name,         FOREIGN_SCHEMA = OBJECT_SCHEMA_NAME(parent_object_id),         FOREIGN_TABLE = OBJECT_NAME(parent_object_id),         REFERENCED_SCHEMA = OBJECT_SCHEMA_NAME(referenced_object_id),         REFERENCED_TABLE = OBJECT_NAME(referenced_object_id)  FROM sys.foreign_keys WHERE OBJECT_NAME(referenced_object_id) = 'MyTable'; GO   but I am struggling now to get the explicit column references.  I am creating a script generator for QlikView. To generate the script I need the constraints and the associated links. I need all of the constraint information for any given column (if any).  I want to construct a database class that holds all the information for a given database. This class structure database.table.column.constraints will then be used to get the matches between different columns on PK/FKs.  Clearly some columns will have FKs only and in this case I also want to retrieve the PK information of the corresponding key; some will have only PKs and then I want the reverse. Some of course can have both.


I've created a random question generator. All questions are in the form: x=3/random number. The problem is that the program never recognizes the fact that the user's answer is correct. I've made it print out the answer and copy it into the answer input (text pane), yet it always prints out "wrong."   private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                               //Generates random value for n (2 decimal plcae)        double nMin = 1.0;//minimum     double nMax = 38.6;//maximum     Random rn = new Random();       double nRand = nMin + (nMax - nMin) * rn.nextDouble();      //Calculates corresponding value of v     String x = String.format("%.2f", 3/nRand );     double nAns = Double.parseDouble(x);//corresponding value of c     check.setText(x);      //displays question     question.setText("n = " + String.format( "%.2f", nRand ) + "     v = ?");//question     String answer = answerInput.getText();     Double nUserA = Double.parseDouble(answer);     //checks user's answer     if(x.equals(answer)) {         check.setText("correct");     }         else         check.setText("wrong");     }

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


What I'd like to know is how we can resolve the two statements, "Circuits/linear components will only draw what they need", and "V = IR". They seem to contradict one another, in my view. With a given voltage and a given resistance, current will be set by these two properties in the circuit, regardless of "the current components need". If this could be at all explained mathematically as well, I also think that'd be better... these analogies seem limited after a certain depth...

In a previous question, it was brought to me that LEDs do not obey the Ohm's law. (See )  Simply put: how is that?  What makes them behave so differently? How should we treat them in a circuit and calculations?  Are there other components with similar behavior?


I want to prove that, for any $t$, a solution exists in the interval $[0,T]$, when $T>0$.  $x'(t)=A(t)x(t)$  My question is quite similar to this one , but with one small difference. My $A(t)$ is a function of $t$, whereas in the other question $A$ seems to be constant.  Picard iteration: $x^{[k+1]}=x_0+\int^t_0A(τ)x^{[k]}(τ) dτ$. Where $x_0$ is arbitrary.  I want tor prove that $x^{[k+1]}$ converges on the given interval and that it satisfies the equation below.  $|x^{[k+1]}(t)-x^{[k]}(t)|\le |x_0| $$\frac{π^{k+1}(t)}{(k+1)!}$ where $π(t)=\int^t_0||A(τ)||dτ$.  I'm not sure how to account for the variant function $A(t)$ in my proof, so I was hoping someone could show me what it look like

I looking at a time variant first order system. I am trying to prove that a sequence of functions $x^{[k]}(t)$ generated using Picard iterations converges uniformly on some interval $[0,T]$.  Given:  $\dot{x}(t)=A(t)x(t)$ where $x(0)=x_0$  $x(t)=x∈R^n$ where $A(t)$ is a $n×n$ matrix  Assume there exists $M$ such that $||A(t)||\le M$ for all $t\ge 0$ and that $A(t)$ is a piecewise continuous function. Show that, for any $T > 0$, a solution exists in the interval $[0,T]$.  I know that $x(t)=x_0+\int^t_0A(τ)x(τ) dτ$ must be satisfied if the solution does indeed exist.  I am supposed to use Picard iterations to prove this, which I am not familiar with yet. But I know that they are of the form: $x^{[k+1]}=x_0+\int^t_0A(τ)x^{[k]}(τ) dτ$. Where $x^{[0]}(t)=x_0$  Can I use the standard Picard proof to prove this or do I need to start somewhere else?  I was also asked to show that this method satisfies  $|x^{[k+1]}(t)-x^{[k]}(t)|\le |x_0| $$\frac{π^{k+1}(t)}{(k+1)!}$ where $π(t)=\int^t_0||A(τ)||dτ$.  I have no idea where to start with this, but hopefully it will become clearer once I finish the first part.


I have several text files which should contain text in multiple lines. I can see that the \n is present where the text should go to a new line, but this is not working. I also noticed that there is no space between the \n and the following word (i.e. word1 \nword2) could this be the cause? How can I solve this?  I tried to modify manually one of the files (by changing the \n with an actual "return") and this worked, but I have hundreds of files. I would like to use sed, but I don't know how to change \n to "return".

I'm so confused with GNU sed, POSIX sed, and BSD sed's myriad of options.  How do I replace literal \n with the newline character using these three sed types?


I apologize in advance if this already has an answer but the best I could find relevant was:   Which is not exactly what I am looking for.  I am trying to figure a regex for a fixed string ending with number.   So lets say my fixed string is "This is Sparta"  So the regex would match for   "This is Sparta9" "This is Sparta100" "This is Sparta87" "This is Sparta21" "This is Sparta8"  But will not match for anything else before and after the string so  "This is Sparta7e" would not match "Hi, This is Sparta7" would not match "This is Sparta and 7" would not match  So basically a fixed String (CONSTANT) ending with number is the kind of regex I am looking for.

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


Is it possible to accomplish in Linux the functionality of Windows Virtual Router ()?   In another words, i want to have a NIC connected to an access point, and the same NIC acting as an access point. Is there anyone that have done such a thing in Linux?  Many thanks.

I am trying to create a WiFi hotspot or an access point on my Linux laptop. I am using Opensuse Kde 12.3.  I found out a software called hostapd which lets you create hotspot but it requires two interfaces. One connected to the internet and the other on which you want to create the access point () . The problem I have is that I don't have Ethernet connection. The wlan interface is being used to connect to the internet.   Is there any way to create the hotspot on the same interface that is connected to the Internet (like the software connectify does on Windows)? I was thinking of creating a virtual interface (like the one airmon-ng creates to monitor wifi) and use it as the second interface. Is this possible?  UPDATE  Here's what i have been able to do up till now :  1) Create 2 interfaces ( one as station and the other as an access point )    iw phy phy0 interface add mySta type station   iw phy phy0 interface add myAcc type __ap   2) Give them seperate Mac ID   ifconfig myAcc hw ether A4:17:FE:6E:00:53 ifconfig myAcc 192.168.27.1 up   3) start hostapd on the myAcc interface  4) start dnsmasq to provide ip address to the connecting devices  All of this works. Devices are able to connect to this network and obtain Ip Address.  The next step is to provide ip masquerading   iptables --table nat --append POSTROUTING --out-interface mySta -j MASQUERADE iptables --append FORWARD --in-interface myAcc -j ACCEPT   But the mySta interface now fails to connect to the internet. It is able to obtain the Essid but it cannot obtain the ip address.  The command dhclient mySta doesn't show any message and after some time gives the error :  ls: cannot access /var/run/netconfig//mySta/: No such file or directory   Can someone figure out how to obtain the ip address ?


Can an Indian national travel to Mexico in F1 visa?I also have an B1/B2 visa but I am residing in US currently in F1 status. And what about people with H1B visas?

My parents have B1/B2 visa and do they need Mexico visa if they want to visit Mexico (<10 days) during their stays at US?  When I had H1b visa, I visited Mexico without any Mexico visa. Again the same thing also goes with F1 visa. But I'm not sure about B1/B2 visa.  Any links or references would be really helpful.


I have a quartz crystal and I am connecting it to a microcontroller's EXTAL and XTAL pins.    Can I connect it anyway? Do the crystals have polarity? In EXTAL and XTAL, which is input and which is output pins?

I am using TXC 7B 16.0 mghz crystal for my design. I just received photo proofs from my PCB assembly house and it appears they soldered this crystal 180.0 degrees reversed.     Edit: the real


Say, there are 2 stationary electrons placed at a distance. The result of observation would be both flying apart with the same speed and the opposite direction, which would obey laws of conservation of momentum and energy (as electric potential energy is converted into kinetic energy). But if considered from the perspective of emitting and receiving photons, how is the process like? Where does the energy come from? Does the mass of either electron change? Or should I not try to understand it from the classic point of view?

I hope this is the right word to use.  To me, these forces seem kind of fanciful (except for General Relativity and Gravity, which have a geometric interpretation).  For example, how do two charged particles know that they are to move apart from each other?  Do they communicate with each other somehow through some means?  I've heard some people tell me that they bounce together messenger photons.  So does one electron receive a messenger photon, go, "Oh hey, I should move in the direction opposite of where this came from, due to the data in it", and then move?  Aren't photons also associated with energy, as well?  Does this type of mediation imply that electrons give off energy in order to exert force on other electrons?  Every electron is repelled by every other electron in the universe, right?  How does it know where to send its force mediators?  Does it just know what direction to point it in?  Does it simply send it in all directions in a continuum?  Does that mean it's always giving off photons/energy?  I'm just not sure how to view "how" it is that electrons know they are to move away from each other.  These questions have always bugged me when studying forces.  I'm sure the Standard Model has something to shed some light on it.


Ever since I found designs that has this warped shadow effect I couldn't stop trying it out and see if I could do it. I've already done my research and I can't seem to get it perfectly. I'm trying to achieve this:   I'm trying to achieve that shadow effect below the large image. It's on the green background. But so far this is what I came up with:    I don't think it's the same as the first image. Well, it's not really the same cause the shadow on the first picture is on a green background but I'm saying, it's really not perfect like the first one. Please tell me how to make this perfectly. I know there are a lot of ways to achieve this but I am really running out of ideas. I already tried every method I know of.  I already checked the said "duplicate". It's quite not the same as what I'm trying to achieve. I wanna achieve the first image's shadow PERFECTLY not similarly. I've already gotten it similarly now I wanna achieve it perfectly.  Here's more of what I came up with:    Okay, so this question is about modifying curved shadows to simulate a bulge that lifts high enough for some light scatter to soften the middle of the shadow. - user568458  ^ that is exactly the problem. Thank you for pointing it out for me user568458   An update:    It's still not perfect but this is what I came up with trying what user568458's suggestion.

How to create the shadow effect like the URL/image below? Specifically, the rounded/curved shadow at the bottom:


I would like to type  < X >  without the spaces. Doing so (at least without the first space) yields no character at all.  Typing the same in code mode works:  <X>

I've posted a lot to StackOverflow, and I've noticed something kind of irritating with the formatting in writing questions and comments. If I need to put something inside a < and a >, without spaces in the middle (like right there), it will think it's code and not show up, like this   (obviously it won't come up what I wrote there, or else this wouldn't be an issue, but if you open up the question to edit you can see what's written there.)  If I want it to show up, right now I have to add an extra set of brackets inside of the originals with a junk variable, like right <here> (again, open in edit window to see).  This is really annoying when trying to show variables like lists that require those brackets, and I feel like the junk variables could confuse people looking at the edits. Is there a way to get around this formatting? Thanks!


I have two raster files in ArcGIS 10.1, raster 1 and raster 2 all with values and similar spatial resolutions, and overlay in some areas.   I want to replace values in raster 1 with those in raster 2 where there is an overlay.

I have two rasters (raster1 and raster2). The raster1 extent is smaller than raster2. I want to replace the value of raster2 pixels using raster1 pixels. How can I replace the values?


I've seen various  about how you cab hide stray elements like this with aura components, and I think the answer with LWC is always 'shadow-dom' as described   but is there really no way to hide the help icon on a Lightning Input Field when you set the label to be hidden?   <lightning-input-field  key={item.submittedDataField}  field-name={item.submittedDataField}  onchange={onInputChange} title={item.submittedDataField}  variant="label-hidden" > </lightning-input-field>   The label is hidden but it still shows the help icon:    I can see the element I think I want to hide in the Chrome Dev Console:    But no combination of css seems to be able to hide it e.g.  .slds-form-element__icon {     display: none !important; }  :host (.slds-form-element__icon) {     display: none !important; }

How can I change the colors of lightning-button?  I tried doing this in my css:  .my-button {     background-color: #14a6bc;     color: #ffffff; }   and applying that class to my <lightning-button> and removing the variant but I still get the base colors? I am trying to use these examples:


The Poor Man’s Introduction to Tensors - by Justin C. Feng.      On page 3, "Before I can tell you what a tensor is, I must tell you what a vector really is; in fact, you will later see that a vector is a type of tensor. A vector is simply a directional derivative. Before you write me off as a nut, take a look at the directional derivative of some scalar function $f(x^i)$"  $$\nu.\nabla(f(x^j))=\nu^i\dfrac{\partial}{\partial{x^i}}f(x^j)$$  To me this is still ok, the author later removes the function itself and claim,  $$\nu.\nabla=\nu^i\dfrac{\partial}{\partial{x^i}}$$ currently i see $\nu.\nabla$ as some form of operator.  But my trouble arises when on page 4, equation 19, author then gives equation, stating the following "Some people get rid of the function f altogether, and write the following:"  $$\nu=\nu^i\dfrac{\partial}{\partial{x^i}}$$ and $$\nu^i = \nu(x^i)$$  My problem is that seem that this definition of vector seems very un-intuitive to me,maybe because i am acquainted with all the old definition. It is as if vector were a operator. Can anyone give me the intuition behind this? Or can someone help me make its sense in term of old definitions of vector i have like in simple Euclidean geometry.  Edit: Just to be exact from the possible duplicate, My problem with intuition is exactly this new operator kind of definition As compared to n-tuple that i have been seeing all along. Exactly how do they connect if they do so, Or if they are different or if one generalizes the other.

I've been reading the book Gauge, Fields, Knots and Gravity by Baez.  A tangent vector at $p \in M$ is defined as function $V$ from $C^{\infty}(M) $ to $\mathbb R$ satisfying the following properties:   $V(f+g)=V(f) + V(g)$. $V(\alpha f)= \alpha V(F)$. $V(fg) = V(f)g(p) + V(g)f(p)$.   Can someone explain me what is the physical interpretation of tangent vectors and the above definition?


As I understand, friction arises from electromagnetic forces. Electric fields, at least static ones, exert conservative forces. So how is it that friction is non-conservative?

Consider the mysterious force of friction. It drives our cars and bikes, slows them down, allows me to walk to the nearest dominoes store, allows me to eat my delicious pizza while ensuring that I stay sitting on the amazing seats provided by the pizza store.  Now friction is a non-conservative force we all know that amount of work done in dragging a body across a carpet depends on the exact route you take. However along with this practical experience I have also been taught that most interactions between everyday objects are a consequence of electromagnetic force which is conservative in nature. So my question how do several different Electromagnetic forces come together to make a new frictional force which is non-conservative in nature


I want to create a new instance of a class type only known at runtime, and cast it, based on a given object. I have an "if" statement to make it, since the possible class types are known. However this doesn't seem like a good way to make mantainable or even efficient code. Is there a better way to do this in c# ?  if (car.Color.GetType().ToString() == "My.Domain.ColorBlue")  {     ColorBlue color = new ColorBlue(); } else if (car.Color.GetType().ToString() == "My.Domain.ColorRed") {     ColorRed color = new ColorRed(); }   car.Color = color;    return PartialView("XPTO.cshtml", car);   I want to pass the derived class to a MVC View, so I really need it to be casted to the correct type. The view then calls one of many other possible partial views:             if (viewDatatype == "My.Domain.ColorBlue")             {                 Html.RenderPartial("XPTOBlue.cshtml", @Model.Color);             } else if(viewDatatype == "My.Domain.ColorRed") (...)   and these partial views are strongly typed to one of the derived classes, for example:  @model My.Domain.ColorBlue

Is there a way to create an instance of a class based on the fact I know the name of the class at runtime. Basically I would have the name of the class in a string.


HI friends i need little help to resolve this error  public CloneContractCtrlr(ApexPages.StandardController controller) {         //objCntrct= new Contract();       objCntrct= new Contract();      String recId = ApexPages.currentPage().getParameters().get('conid');       objCntrct = [Select Id, Name, Opportunity__c,Forecast_Date__c,Capital_Business_Owner__c,OwnerId  FROM Contract where id =:recId limit 1];                system.debug('objCntrct--ct--'+objCntrct);      objCntrct.Capital_Business_Owner__c = objCntrct.OwnerId;                           //system.debug('objCntrct123----'+objCntrct.Capital_Business_Owner__c);   }

I have this controller but I am getting this error      System.QueryException: List has no rows for assignment to SObject   public class MyController {     private final Account account;      public MyController() {         account = [SELECT Id, Name, Site FROM Account                     WHERE Id = :ApexPages.currentPage().getParameters().get('id')];             }      public Account getAccount() {         return account;     }      public PageReference save() {         update account;         return null;     } }