[R] Grep command

[Peter Langfelder]

I use my own functions multiGrep and multiGrepl:

multiGrep = function(patterns, x, ..., sort = TRUE, invert = FALSE)
{
  if (invert)
  {
    out = multiIntersect(lapply(patterns, grep, x, ..., invert = TRUE))
  } else
    out = unique(unlist(lapply(patterns, grep, x, ..., invert = FALSE)));
  if (sort) out = sort(out);
  out;
}

multiGrepl = function(patterns, x, ...)
{
  mat = do.call(cbind, lapply(patterns, function(p)
as.numeric(grepl(p, x, ...))));
  rowSums(mat)>0;
}

> multiGrep(some, all)
[1] 1 3 6

> multiGrepl(some, all)
[1]  TRUE FALSE  TRUE FALSE FALSE  TRUE

multiGrep(some, all, invert = TRUE)
[1] 2 4 5

Peter


On Thu, May 19, 2016 at 4:09 PM, Steven Yen <syen04 at gmail.com> wrote:
> What is a good way to grep multiple strings (say in a vector)? In the
> following, I grep ants, cats, and fox separately and concatenate them,
> is there a way to grep the trio in one action? Thanks.
>
> all<-c("ants","birds","cats","dogs","elks","fox"); all
> [1] "ants"  "birds" "cats"  "dogs"  "elks"  "fox"
> some<-c("ants","cats","fox"); some
> [1] "ants" "cats" "fox"
> j<-c(
>    grep(some[1],all,value=F),
>    grep(some[2],all,value=F),
>    grep(some[3],all,value=F)); j; all[j]
> [1] 1 3 6
> [1] "ants" "cats" "fox"
>
>
>         [[alternative HTML version deleted]]
>
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