On Feb 13, 2014, at 8:43 AM, Rainer M Krug <[email protected]> wrote:
> Hi
>
> I want to search for multiple pattern as grep is doing for a single
> pattern, but this obviously not work:
>
>> grep("an", month.name)
> [1] 1
>> grep("em", month.name)
> [1] 9 11 12
>> grep("eb", month.name)
> [1] 2
>> grep(c("an", "em", "eb"), month.name)
> [1] 1
> Warning message:
> In grep(c("an", "em", "eb"), month.name) :
> argument 'pattern' has length > 1 and only the first element will be used
>>
>
> Is there an equivalent which returns the positions as grep is doing, but
> not using the strict full-string matching of match()?
>
> I could obviously do:
>
>> unlist( sapply(pat, grep, month.name ) )
> an em1 em2 em3 eb
> 1 9 11 12 2
>
> but is there a more compact command I am missing?
>
> Thanks,
>
> Rainer
The vertical bar '|' acts as a logical 'or' operator in regex expressions:
> grep("an|em|eb", month.name)
[1] 1 2 9 11 12
> grep("an|em|eb", month.name, value = TRUE)
[1] "January" "February" "September" "November" "December"
Regards,
Marc Schwartz
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