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Re: Better Way of Testing and Replacing List Elements?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg103972] Re: [mg103949] Better Way of Testing and Replacing List Elements?
  • From: Leonid Shifrin <lshifr at gmail.com>
  • Date: Wed, 14 Oct 2009 07:55:43 -0400 (EDT)
  • References: <200910140319.XAA22469@smc.vnet.net>

Hi,

You may skip Mapping since Negative is listable - this may give you some
speedup:

ReplacePart[xxx, Position[Negative@xxx, True] -> 0]

If your list is large, ReplacePart may slow down. Even faster is

xxx /. _?Negative :> 0

Still, the best and fastest way to do it is probably this:

Clip[xxx, {0, Infinity}]


Regards,
Leonid




On Wed, Oct 14, 2009 at 7:19 AM, careysub <careysub at gmail.com> 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.
>
>



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