Re: Selecting Rows Where All Columns Satisfy a Condition
- To: mathgroup at smc.vnet.net
- Subject: [mg82627] Re: Selecting Rows Where All Columns Satisfy a Condition
- From: Ray Koopman <koopman at sfu.ca>
- Date: Fri, 26 Oct 2007 05:28:04 -0400 (EDT)
- References: <ffppu6$l6g$1@smc.vnet.net>
On Oct 25, 3:08 am, 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
Select[X, FreeQ[#,-9]&]
is compact, easily understood, and about 50% faster than your code.
X[[ SparseArray[Times@@(Transpose@X + 9)] /.
SparseArray[_, _, _, p_] :> Flatten@p[[2,2]] ]]
is long, arcane, and about 35 times faster.