       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[#[] > 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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