I have a character vector like this:
id <-c("A01A01", "A01B01", "A01C01", "R", "S", "T")
I need to cut a prefix from all the strings that contains it, keeping all the substrings My expected output are then 2 other vectors like these:
a <-c("A01", "A01", "A01", "", "", "")
b <-c("A01", "B01", "C01", "R", "S", "T")
You can use sub like:
sub("^(A01).*|.*", "\\1", id)
#[1] "A01" "A01" "A01" "" "" ""
sub("^A01", "", id)
#[1] "A01" "B01" "C01" "R" "S" "T"
where ^(A01).*|.* matches A01 in the beginning or everything and \\1 inserts A01 if it matches.
Another option would be a look behind in strsplit.
strsplit(id, "(?<=^A01)", perl=TRUE)
Does this work:
a <- sapply(id, function(x) if(nchar(x)%%2 == 0) substr(x, 1,nchar(x)/2) else '', USE.NAMES = FALSE)
b <- sapply(id, function(x) if(nchar(x)%%2 == 0) substr(x,nchar(x)/2+1, nchar(x)) else x,USE.NAMES = FALSE)
a
[1] "A01" "A01" "A01" "" "" ""
b
[1] "A01" "B01" "C01" "R" "S" "T"
An option with extract from tidyr
library(tidyr)
library(dplyr)
tibble(id) %>%
extract(id, into = c('a', 'b'), '(A01)?(.*)')
# A tibble: 6 × 2
a b
<chr> <chr>
1 "A01" A01
2 "A01" B01
3 "A01" C01
4 "" R
5 "" S
6 "" T