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What is the fastest way to threshold data?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85898] What is the fastest way to threshold data?
  • From: "Kevin J. McCann" <Kevin.McCann at umbc.edu>
  • Date: Wed, 27 Feb 2008 04:24:39 -0500 (EST)
  • Organization: University System of Maryland

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
-- 

Kevin J. McCann
Research Associate Professor
JCET/Physics
Physics Building
University of Maryland, Baltimore County
1000 Hilltop Circle
Baltimore, MD 21250


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