Lecromine - 4 months ago 28

R Question

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.

Answer

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)]
```