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Re: Simply but handy question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124844] Re: Simply but handy question
  • From: Christoph Lhotka <christoph.lhotka at fundp.ac.be>
  • Date: Thu, 9 Feb 2012 05:38:21 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201202081029.FAA06451@smc.vnet.net>

hi, if you really need the matrix use a pattern rule like:

Y/. x_Integer :> 1 /; NumericQ[x]&&x != 0

which will replace all non-zero values with one.

if you just need to know the position of the zeros use

Position[Y, 0, \[Infinity]]

which will return a list of positions in Y which are zero.

best,

christoph

On 02/08/2012 11:29 AM, jediwhelan wrote:
> Dear group members,
>
> I am new to mathematica (well, I'm not actually but I haven't used it
> in 5 years +).
>
> Is there an easy way to return a matrix X of 1's and 0's to test
> whether the entries in Y
> are different from zero.
>
> i.e.,
>
> if Y = {{a,b},{0,c}}
>
> Then X would return
>
> X = {{1,1},{0,1}}
>
> This would be handy for very large or complicated matrices where one
> would like to know if specific entries are zero?
>
> Many thanks,
> Paul
>




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