Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2002
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Pattern matching

  • To: mathgroup at smc.vnet.net
  • Subject: [mg33961] Re: Pattern matching
  • From: bghiggins at ucdavis.edu (Brian Higgins)
  • Date: Wed, 24 Apr 2002 01:22:51 -0400 (EDT)
  • References: <aa3fq4$7tv$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

John, Perhaps this will be more efficient:

myfunc[data_, template_] := 
  Flatten[Map[Function[w, Select[data, MatchQ[Characters[#], w] &]], 
      Characters[template] /. "?" -> _]]
In[30]:=myfunc[listData,listTemplates]

Out[30]={400HGXX--,960KG1D--}

Cheers,

Brian


John Leary <leary at paradise.net.nz> wrote in message news:<aa3fq4$7tv$1 at smc.vnet.net>...
> Greetings
> 
> Can you help me please - there must be a simple solution to this problem, 
> but I can't find it.
> 
>  From a list of character strings and a list of templates,  I need to 
> produce a list of all strings that match any of the templates.  For example:
> 
> listData={"18K0F3C--" , "2K40GXX--" , "400HGXX--" , "5M00G1F--" , "960KG1D--"}
> listTemplates={"???H?????" , "???K?????"}
> result={"400HGXX--","960KG1D--"}
> 
> In the templates, ? is a wild-card that represents a single character.
> The data strings contain only alpha-numeric characters and hyphens - no 
> other characters.
> There are no special requirements for the result:  duplication and random 
> order are acceptable.
> 
> 
> I searched the MathGroup archive and found a very useful function that does 
> exactly what I want, but it works only on individual strings, not lists of 
> strings (msg00051):
> 
> QMMatchQ[s_String, p_String] := MatchQ[Characters[s], Characters[p] /. "?" 
> -> _ ]
> 
> 
> 
> I tried to use it in the following way, but the result is a list of the 
> matching templates, not the matching strings :
> 
> QMMatchQ[s_String, p_String] := MatchQ[Characters[s], Characters[p] /. "?" 
> -> _ ]
> SetOptions[Intersection, SameTest -> (QMMatchQ[#1,#2]& )];
> result=Intersection[listData,listTemplates]
> {"???H?????","???K?????"}
> 
> 
> It ought to be a small step from there to the result that I need, but I 
> can't find a simple solution.
> 
> One alternative approach would be a Do loop:
> 
> b={};
> Do[b=Append[b,Select[listData,QMMatchQ[#,listTemplates[[n]]]&]],{n,1,Length[listTemplates]}]
> 
> This works but seems to be very slow for large lists.  In the real case, 
> listData can be very large - up to 250,000 elements - and the Do loop 
> approach doesn't seem to be optimum.
> 
> 
> I would be very grateful for your help.
> 
> 
> Regards
> 
> John Leary


  • Prev by Date: RE: Pattern matching
  • Next by Date: RE: Pattern matching
  • Previous by thread: RE: Pattern matching
  • Next by thread: RE: Pattern matching