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Re: What is the fastest way to threshold data?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85922] Re: What is the fastest way to threshold data?
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 28 Feb 2008 02:41:16 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <fq3af1$fot$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

With[{nn = 64},
   data = Table[RandomReal[{-1, 1}], {nn}, {nn}, {nn}, {3}]
   ];

and

thdata = Map[If[#[[3]] > 0, #, {1, 1, 0}*#] &, data, {3}];

may help

Regards
   Jens

Kevin J. McCann wrote:
> I have some 3d data {{x1,y1,z1},{x2,y2,z2},...} and I would like to set 
> the z-values to zero if they fall below zero. More generally, I would 
> like to set z to a threshold value if it is at or below a threshold. 
> This seems as though it should be an easy enough thing to do, but the 
> only way I have figured out is to parse out the z-vector, do
> 
> mask=((#<thresh&) /@ zdata)/.True->0/.False->1;
> 
> then
> zvector = zvector*mask;
> 
> and rebuild the {x,y,z} data.
> 
> Kevin


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