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Re: position of matrix elements for intervals

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78439] Re: position of matrix elements for intervals
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Mon, 2 Jul 2007 06:41:20 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <f68491$eqh$1@smc.vnet.net>

kristoph wrote:
> Hi,
> 
> Assume you have the following table:
> 
> {{1, 1.`, 0.9999999932328848`}, {1.`, 0.9985849617864345`,
>       3.7570598417296495`*^-108}, {0.9999999999267634`,
>       4.0643593704937925`*^-207, 0}}
> 
> I would like the position of all the elements >= 0.99. Or the position
> of all the elements of [0.4, 0.9] which in the above table does make a
> lot of sense.
> I'm familiar with Position[...,.] but since I look for reals of an
> interval I would kindly ask for help.
> 
> Thanks a lot,
> Kristoph

Hi Kristoph,

You could use interval arithmetic as in the following example:

In[1]:=
data = {{1, 1., 0.9999999932328848},
     {1., 0.9985849617864345,
      3.7570598417296495*^-108}, {0.9999999999267634,
      4.0643593704937925*^-207, 0}};

Position[data, x_ /; IntervalMemberQ[
     Interval[{4/10, 10/10}], x]]

Out[2]=
{{1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 2}, {3, 1}}

HTH,
Jean-Marc


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