I have a table like below, it is a bed file of genome coordinate, I would like to keep only rows with numbers.

Input:

    1	        141009669	141009952
    9	        141016322	141016973
    GL000195.1	81719	82468
    GL000195.1	142613	142923
    GL000220.1	119445	119746
    HG115_PATCH 101957832	101958132
    HG1308_PATCH 130205069	130205369
    HG1308_PATCH 130205406	130205773
    HG748_PATCH  77577953	77578264
    X	         200983	202660
    y         205180	205702


output:

    1	        141009669	141009952
    9	        141016322	141016973
    X	         200983	202660
    y	         205180	205702


Thanks in advance!
command line:

```
egrep "^[0-9XY]" file
```
EDIT: originally, this used the same regex as for the R-based example (`^[0-9XY]$`). This won't work because the full line of the text file contains more characters (such as the coordinates...). Thanks to Alex for pointing this out.

R (because this post is tagged with it):

```
# assuming your data frame with the coordinates looks like this
df <- data.frame(chr = c("1","2","X","Y", "GL000220.1"),
                start = c(1,20,30,40,50),
                 end = c(11, 21, 31, 41, 51)
)

subset(df, grepl("^[0-9XY]$", chr))
```