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Re: Picking Off Lists That Have No Numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99523] Re: Picking Off Lists That Have No Numbers
  • From: Ulvi Yurtsever <a at b.c>
  • Date: Thu, 7 May 2009 06:35:07 -0400 (EDT)
  • References: <gtrl29$1o5$1@smc.vnet.net>

Gregory Lypny <gregory.lypny at videotron.ca> wrote in news:gtrl29$1o5$1
@smc.vnet.net:

> Hi everyone,
> 
> In a previous thread, "Select and Cases Give Different Answers," I  
> discussed a bug, confirmed by others on the list and which Daniel  
> Lichtblau of Wolfram said has been fixed in the development kernel,  
> and I wonder whether we have the same problem here.
> 
> I want to know if a list has no numbers in it.  Here I get the wrong  
> answer for the first list.
> 
> FreeQ[#, _Number] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}
> 
> yields {True, True}
> And same here.
> 
> MemberQ[#, _Number] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}
> 
> {False, False}
> 
> If I use Real or Rational for the criterion, I get the right answers,  
> but that's no good if you have some lists that are mixtures of strings  
> and reals and others that are mixtures of strings and rationals.


I don't think _Number is a built-in pattern match,
unlike _Real, _Rational, _String, or _Integer.

You can use _?NumberQ instead:


In[29]:= FreeQ[#, _?NumberQ] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

Out[29]= {False, True}


In[30]:= MemberQ[#, _?NumberQ] & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

Out[30]= {True, False}


In[32]:= 
Count[#, _?NumberQ] == 0 & /@ {{"NA", 2.3, 3/8}, {"NA", "NA", "NA"}}

Out[32]= {False, True}



Ulvi


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