Thank you. I think grep would do it, but the list of expressions I
need to match is too long so they are stored in a file. So the
question would be how I can tell R to look into that file to look for
the expressions that I want to match.
Thank you again for your help
Laura
2009/2/6 Wacek Kusnierczyk <waclaw.marcin.kusnierc...@idi.ntnu.no>:
> Laura Rodriguez Murillo wrote:
>> Hi,
>>
>> I'm new in the mailing list but I would appreciate if you could help
>> me with this:
>> I have a big matrix from where I need to delete specific rows. The
>> second entry on these rows to delete should match any string within a
>> list (other file with just one column).
>> Thank you so much!
>>
>>
>
> here's one way to do it, illustrated with dummy data:
>
> # dummy character matrix
> data = matrix(replicate(20, paste(sample(letters, 20), collapse="")),
> ncol=2)
>
> # filter out rows where second column does not match 'a'
> data[-grep('a', d[,2]),]
>
> this will work also if your data is actually a data frame:
>
> data = as.data.frame(data)
> data[-grep('a', d[,2]),]
>
> note, due to a known issue with grep, this won't work correctly if there
> are *no* rows that do *not* match the pattern:
>
> data[-grep('1', d[,2]),]
> # should return all of data, but returns an empty matrix
>
> with the upcoming version of r, grep will have an additional argument
> which will make this problem easy to fix:
>
> data[grep('a', d[,2], invert=TRUE),]
>
>
> vQ
>
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