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Re: Searching for multiple strings in a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86301] Re: [mg86280] Searching for multiple strings in a list
  • From: Oyvind Tafjord <tafjord at wolfram.com>
  • Date: Sat, 8 Mar 2008 05:39:11 -0500 (EST)
  • References: <200803070730.CAA20006@smc.vnet.net>

Coleman, Mark wrote:
> Greetings,
> 
> I'm doing some work with very long lists of strings. As part of the
> effort I need to identify strings that contain all of set of keywords
> (regardless of order) that a user may specify. The function StringCases
> will take multiple keywords as an argument, but it will return a list
> giving those elements that contain any one of the keywords, not *all* of
> the keywords. I know this can be done using multiple calls to
> StringCases and comparing the results for each keyword, but this seems
> very cumbersome, particularly if there are many keywords specified.
> 
> Any help would be most appreciated.
> 
> 
> Thanks,
> 
> -Mark

Here's a reasonably efficient way:

In[44]:=
list = {"foo foo", "foo bar", "bar foo none",
    "bar foo bar none", "foobar"};
keywords = Union[{"foo", "bar"}];
Pick[list,
  Union /@ StringCases[list,
    WordBoundary ~~ keywords ~~ WordBoundary], keywords]

Out[46]= {"foo bar", "bar foo none", "bar foo bar none"}

Taking advantage of the List support in the first argument of StringCases 
can save a fair amount of time for large lists.

Oyvind Tafjord
Wolfram Research


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