I've got two character vectors:
x = {"a", "b", "c", "kt"}
y = {"abs", "kot", "ccf", "okt", "kk", "y"}
I need to use x to remove entries from y so that only the strings that do not contain any of the x's entries remain, like this:
y = {"kot", "kk", "y"}
The code should work for any size of vectors x and y.
So far I've tried to use gsub and grepl but these only work with single strings. I've tried to create a loop to do this but the problem seems more difficult than I thought. And of course, the more sophisticated the solution is, the better, but you can assume that in this case the vectors x and y have up to 200 entries.
We can use grep
to find out which values in y
match the pattern in x
and exclude them using !%in%
y[!y %in% grep(paste0(x, collapse = "|"), y, value = T)]
#[1] "kot" "kk" "y"
Or even better with grepl
as it returns boolean vectors
y[!grepl(paste0(x, collapse = "|"), y)]
A concise version with grep
using invert
and value
parameter
grep(paste0(x, collapse = "|"), y, invert = TRUE, value = TRUE)
#[1] "kot" "kk" "y"
The answer given by @Ronak looks preferable to mine, but one option is to use sapply
with grepl
to get a matrix of matches against y
, for each entry in x
, then to roll that up with another call to apply
.
> y[!apply(sapply(x, function(q) {grepl(q, y)}), 1, function(x) {sum(as.numeric(x)) > 0})]
[1] "kot" "kk" "y"
Here is what I mean by matrix of matches:
> sapply(x, function(q) { grepl(q, y) })
a b c kt
[1,] TRUE TRUE FALSE FALSE
[2,] FALSE FALSE FALSE FALSE
[3,] FALSE FALSE TRUE FALSE
[4,] FALSE FALSE FALSE TRUE
[5,] FALSE FALSE FALSE FALSE
[6,] FALSE FALSE FALSE FALSE
^^^^ each column is a match result for each element of x
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