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
>