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Re: Better Way of Testing and Replacing List Elements?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103979] Re: [mg103949] Better Way of Testing and Replacing List Elements?
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Wed, 14 Oct 2009 07:57:00 -0400 (EDT)
  • References: <200910140319.XAA22469@smc.vnet.net>

On 14 Oct 2009, at 12:19, careysub wrote:

> The code below replaces the negative values in a list with zero, and
> is an example of a type of operation I use a lot:
>
> xxx = {1, 2, 3, 4, 5, -6, -7, 8, 9, 10, -1, 11, 12};
> ReplacePart[xxx, Position[Map[Negative, xxx], True] -> 0]
>
> Is there a "better" way of doing this (fewer function calls, more
> efficient)?
>
> My feeling is that I'm doing this in an awkward way.
>

For example:
  xxx /. _?Negative -> 0

  {1,2,3,4,5,0,0,8,9,10,0,11,12}

or

xxx*UnitStep[xxx]

{1,2,3,4,5,0,0,8,9,10,0,11,12}

Andrzej Kozlowski


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