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Re: Selecting Rows Where All Columns Satisfy a Condition

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82589] Re: Selecting Rows Where All Columns Satisfy a Condition
  • From: Norbert Marxer <marxer at mec.li>
  • Date: Fri, 26 Oct 2007 05:08:32 -0400 (EDT)
  • References: <ffppu6$l6g$1@smc.vnet.net>

On 25 Okt., 12:08, Gregory Lypny <gregory.ly... at videotron.ca> wrote:
> Hello everyone
>
> I've got an Nx4 numeric array called X.  I'd like to pull out all  
> rows where -9 does not appear in any of the four columns.  I know I  
> can this:
>
> Select[X, #[[1]] != -9 && #[[2]] != -9 && #[[3]] != -9 && #[[4]] !=  
> -9 &]
>
> But is there a more elegant way that applies the not-equal-to  
> condition to each column without having to repeat it?
>
> Regards,
>
>         Gregory

Hello

You could use:

    Select[X, And @@ (#1 != -9 & ) /@ #1 & ]

The following is a short test of the above code and shows that you get
the same result:

r := RandomInteger[{-10, -1}]; SeedRandom[1]; X =  Table[{r, r, r, r},
{10}];
Select[X, #1[[1]] != -9 && #1[[2]] != -9 && #1[[3]] != -9 && #1[[4]] !
= -9 & ] ==  Select[X, And @@ (#1 != -9 & ) /@ #1 & ]

Best Regards
Norbert Marxer




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