Remove just strings from the entries in my first column of data frame

I have strings and numbers in my first column of a data frame:

rn

AT457

X5377

X3477

I want to remove just the strings and keep the numbers from each entry in the column called rn.

Any help is appreciated.

>Solution :

Use a regular expression to do this.

For example, with R :

## Sample data :
df=data.frame(rn=c("AT457","X5377","X3477"))

## Replace the letters with *nothing* ('\D' is used to identify non-digit characters)
df$rn_strip=gsub('\\D',"",df$rn)

## Output :

     rn rn_strip
1 AT457      457
2 X5377     5377
3 X3477     3477