How to convert "A01" to "A1" using R?

Question

As the first step I tried to get the middle character in the string but I couldn't.

STR <- "A01"
p <- as.character(substr(STR,2,1))

I get the following for p. I am very new to R. Please advice me.

[1] ""

What's the general rule you want to follow? Will all your values start with exactly one letter? — MrFlick, Mar 14 '17 at 20:50
I tried that. When it is "A10", then it should not make it "A1". It has to be "A10". Any help? — RanonKahn, Mar 14 '17 at 20:51
Yes it will be one letter in the beginning of the string like "A01"..."A12". I just want to remove the middle 0. — RanonKahn, Mar 14 '17 at 20:55

score 4 · Accepted Answer · answered Mar 14 '17 at 20:50

4

You can use lookaround to replace 0 values:

sub('(?<![0-9])0*(?=[0-9])', '', STR, perl=TRUE)
[1] "A1"

The expression matches all 0 characters that are not preceded by a number, but are followed by a number.

sub('(?<![0-9])0*(?=[0-9])', '', 'A0010', perl=TRUE)
[1] "A10"

sub('(?<![0-9])0*(?=[0-9])', '', 'A00', perl=TRUE)
[1] "A0"

answered Mar 14 '17 at 20:50

Matthew Lundberg

score 4 · Answer 2 · answered Mar 14 '17 at 21:05

4

We can also do this without regex lookarounds

sub("([A-Z]+)0*([0-9]+)", "\\1\\2", c("A01", "A0010", "A00"))
#[1] "A1"  "A10" "A0"

answered Mar 14 '17 at 21:05

akrun

2 Answers2