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Re: What is the fastest way to threshold data?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85955] Re: What is the fastest way to threshold data?
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Thu, 28 Feb 2008 02:58:23 -0500 (EST)

On 2/27/08 at 4:24 AM, Kevin.McCann at umbc.edu (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.

Using the built in function Clip is undoubtedly faster.

Clip[zvector,{0, Infinity}]

will return the values you want.
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