Removing string parts between substrings when substrings occur multiple times in R

Question

In a string

string="aaaaaaaaaSTARTbbbbbbbbbbSTOPccccccccSTARTddddddddddSTOPeeeeeee"

I would like to remove all parts that occur between START and STOP, yielding

"aaaaaaaaacccccccceeeeeee"

if I try with gsub("START(.*)STOP","",string) this gives me "aaaaaaaaaeeeeeee" though.

What would be the correct way to do this, allowing for multiple occurrences of START and STOP?

score 3 · Accepted Answer · answered Mar 02 '14 at 16:35

3

Add a ? in there too.

gsub("START.*?STOP", "", string)
# [1] "aaaaaaaaacccccccceeeeeee"

answered Mar 02 '14 at 16:35

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score 0 · Answer 2 · answered Mar 03 '14 at 02:23

Not nearly as elegant as Ananda's answer, but there are some other ways using the stringr & plyr packages.

library(stringr)
library(plyr)

start <- ldply(str_locate_all(string, 'START'))[1, 1]
end <- ldply(str_locate_all(string, 'STOP'))
end <- end[nrow(end), 2]
expression <- str_sub(string, start, end)
str_replace(string, expression, '')

Removing string parts between substrings when substrings occur multiple times in R

2 Answers2