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Re: Setting Negatives to Zero

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82769] Re: Setting Negatives to Zero
  • From: "Steve Luttrell" <steve at _removemefirst_luttrell.org.uk>
  • Date: Tue, 30 Oct 2007 05:46:13 -0500 (EST)
  • References: <fg6qha$dj0$1@smc.vnet.net>

These do the sort of thing you want

{1, 2, -3, -4, 5, 6} /. {_?(# < 0 &) -> 0}

{1, 2, -3, -4, 5, 6} /. {_?NonPositive -> 0}

and both give


-- 
Steve Luttrell
West Malvern, UK

"Kevin J. McCann" <Kevin.McCann at umbc.edu> wrote in message 
news:fg6qha$dj0$1 at smc.vnet.net...
>I have a very large data set (64000 x 583) in which negative values
> indicate "no data", unfortunately these negatives are not all the same.
> I would like to efficiently set all these negatives to zero. I know that
> I will likely be embarrassed when I see how to do it, but I can't seem
> to remember or figure it out. I should emphasize that because of the
> size of the data set, this needs to be done efficiently. Another
> programming language does it as follows:
>
> x(x < 0) = 0;
>
> Thanks,
>
> 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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