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Re: What is the fastest way to threshold data?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85959] Re: [mg85898] What is the fastest way to threshold data?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 28 Feb 2008 03:00:27 -0500 (EST)
  • Reply-to: hanlonr at cox.net

data /. {x_, y_, z_?Negative} -> {x, y, 0}

or more generally for a threshold

data /. {x_, y_, z_ /; z < threshold} -> {x, y, threshold}


Bob Hanlon

---- "Kevin J. McCann" <Kevin.McCann at umbc.edu> 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
> -- 
> 
> 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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