Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2006
*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 2006

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

Search the Archive

Re: Selecting Lists Without Null Results

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69022] Re: [mg68970] Selecting Lists Without Null Results
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sun, 27 Aug 2006 01:23:42 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

runsTable=Table[Random[],{5},{6}];

runsTable[[2,4]]=Null;
runsTable[[4,4]]=Null;

Length[Select[runsTable, #[[4]] == Null&]]

2

Length[Select[runsTable, ToString[#[[4]]] != "Null"&]]

3


Bob Hanlon

---- Gregory Lypny <gregory.lypny at videotron.ca> wrote: 
> 	I must be doing something wrong as usual.  How come I can select  
> list with elements that have the word Null in them as a result of a  
> computation, but I cannot exclude them?
> 
> I have an array called runsTable with 179 rows, and there are five  
> rows with Null in column 14.
> 
> So,
> 
> 	Length[Select[runsTable, #[[14]] == Null &]
> 
> returns 5.
> 
> But
> 
> 	Length[Select[runsTable, (#[[14]]¬ Null) &]]
> 
> returns 0 when it should return 174, that is, 179 minus 5.
> 
> 	Am I using the NOT operator incorrectly?
> 
> 	Regards,
> 
> 		Gregory
> 


  • Prev by Date: Re: Selecting Lists Without Null Results
  • Next by Date: Re: General--Transformation of coordinates(from carteseian to polar)
  • Previous by thread: Re: Selecting Lists Without Null Results
  • Next by thread: Re: Selecting Lists Without Null Results