I have a dataframe like this:
V1 V2 V3
1 1 3423086 3423685
2 1 3467184 3467723
3 1 4115236 4115672
4 1 5202437 5203057
5 2 7132558 7133089
6 2 7448688 7449283
I want to change the V1 column and add chr before the number. Just like this:
V1 V2 V3
1 chr1 3423086 3423685
2 chr1 3467184 3467723
3 chr1 4115236 4115672
4 chr1 5202437 5203057
5 chr2 7132558 7133089
6 chr2 7448688 7449283
Is there a way to do this in R?
The regex pattern "^" (outside any character-class brackets) represents the point just before the first character of a "character"-class item (aka "string" in other computer languages). This just replaces the beginning of each "character" element in vector with a stem of "chr". It implicitly coerces a "numeric" input value to "character" so alters the mode of the result.
> dat$V1 <- sub("^", "chr", dat$V1 )
> dat
V1 V2 V3
1 chr1 3423086 3423685
2 chr1 3467184 3467723
3 chr1 4115236 4115672
4 chr1 5202437 5203057
5 chr2 7132558 7133089
6 chr2 7448688 7449283
Could, of course, have used paste("chr", dat$V1, sep="")
, but I thought a regex solution might be neater.