title: R: creating a map of selected Canadian provinces and U.S. states
body: <p>I am attempting to create a map of selected Canadian provinces/territories and selected U.S. states. So far the nicest maps appear to be those generated with GADM data: <a href="http://www.gadm.org/" rel="nofollow noreferrer">http://www.gadm.org/</a> </p>
  
  <p>However, I have not been able to plot the U.S. and Canada on the same map or plot only selected provinces/territories and states.  For example, I am interested in Alaska, Yukon, NWT, British Columbia, Alberta, and Montana among others.</p>
  
  <p>Also, the U.S. map appears to be split along the international dateline.</p>
  
  <p>Can someone please help me to:</p>
  
  <ol>
  <li>plot the aforementioned provinces/territories and states on a single map</li>
  <li>avoid having the U.S. split along the International dateline</li>
  <li>overlay a latitude-longitude grid</li>
  <li>select a specific projection, maybe the polyconic.</li>
  </ol>
  
  <p>Maybe spplot does not allow users to specify projections. I did not see an option to select a projection on the spplot help page.  I know how to select projections with the map function in the maps package but those maps did not appear to look as nice and I could not plot the desired subset of provinces/territories and states with that function either.</p>
  
  <p>I do not know how to begin adding a latitude-longitude grid.  However, Section 3.2 of the file 'sp.pdf' seems to address the topic.</p>
  
  <p>Below is the code I have come up with so far.  I have loaded every map-related package I have stumbled upon and commented out GADM data except for provincial/territorial or state boundaries.</p>
  
  <p>Unfortunately, so far I have only managed to plot maps of Canada or the U.S.</p>
  
  <pre><code>library(maps)
  library(mapproj)
  library(mapdata)
  library(rgeos)
  library(maptools)
  library(sp)
  library(raster)
  library(rgdal)
  
  # can0&lt;-getData('GADM', country="CAN", level=0) # Canada
    can1&lt;-getData('GADM', country="CAN", level=1) # provinces
  # can2&lt;-getData('GADM', country="CAN", level=2) # counties
  
  plot(can1)    
  spplot(can1, "NAME_1") # colors the provinces and provides
                         # a color-coded legend for them
  can1$NAME_1            # returns names of provinces/territories
  # us0 &lt;- getData('GADM', country="USA", level=0)
    us1 &lt;- getData('GADM', country="USA", level=1)
  # us2 &lt;- getData('GADM', country="USA", level=2)
  plot(us1)              # state boundaries split at 
                         # the dateline
  us1$NAME_1             # returns names of the states + DC
  spplot(us1, "ID_1")
  spplot(us1, "NAME_1")  # color codes states and
                         # provides their names
  #
  # Here attempting unsuccessfully to combine U.S. and Canada on one map.
  # Attempts at selecting given states or provinces have been unsuccessful.
  #
  plot(us1,can1)
  us.can1 &lt;- rbind(us1,can1)
  </code></pre>
  
  <p>Thanks for any help.  So far I have made no progress with Steps 2 - 4 above.  Perhaps I am asking for too much.  Perhaps I should simply switch to ArcGIS and try that software.</p>
  
  <p>I have read this StackOverflow post:</p>
  
  <p><a href="https://stackoverflow.com/questions/5757058/can-r-be-used-for-gis">Can R be used for GIS?</a></p>
  
  <p>EDIT</p>
  
  <p>I have now borrowed an electronic copy of 'Applied Spatial Data Analysis with R' Bevand et al. (2008) and downloaded (or located) associated R code and data from the book's website:</p>
  
  <p><a href="http://www.asdar-book.org/" rel="nofollow noreferrer">http://www.asdar-book.org/</a></p>
  
  <p>I also found some nice-looking GIS-related R code here:</p>
  
  <p><a href="https://sites.google.com/site/rodriguezsanchezf/news/usingrasagis" rel="nofollow noreferrer">https://sites.google.com/site/rodriguezsanchezf/news/usingrasagis</a></p>
  
  <p>If and when I learn how to accomplish the desired objectives I will post solutions here.  Although I may eventually move to ArcGIS if I cannot accomplish the objectives in R.</p>