Message-ID: <81002AB7-F20A-44B0-86A0-627B1A2B13E5@me.com>
Date: 2014-02-13T15:51:31Z
From: Marc Schwartz
Subject: grep for multiple pattern?
In-Reply-To: <52FCDA05.7090700@krugs.de>
On Feb 13, 2014, at 8:43 AM, Rainer M Krug <Rainer at krugs.de> 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