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MathGroup Archive 2005

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Re: extracting elements from multi-dimensional arrays

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61302] Re: extracting elements from multi-dimensional arrays
  • From: bghiggins at ucdavis.edu
  • Date: Fri, 14 Oct 2005 22:22:32 -0400 (EDT)
  • References: <dio1v0$t01$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Dan, try the following:

In[37]:=
lst=Table[Random[Real,{1,15}],{5},{3}]

Out[37]=
{{5.53554,11.6058,9.73763},{3.45237,7.84251,4.92252},{
  3.30427,13.1812,3.12078},{10.7528,14.8427,12.1167},{
  2.42761,13.2536,8.29897}}

In[39]:=
lst /. {x_Real /; x < 6 || x > 12, y_Real, z_Real} ->
    {y, z} /. {x___Real, y_Real /; y < 4 || y > 12,  z_Real} -> {x, z}

Out[39]=
{{11.6058,9.73763},{7.84251,4.92252},{3.12078},{10.7528,12.1167},{8.29897}}

or if you want to have a tag for those elements deleted you can use

In[41]:=
lst /. {x_Real /; x < 6 || x > 12, y_Real, z_Real} ->
    {0, y, z} /. {x___, y_Real /; y < 4 || y > 12,
    z_Real} -> {x, 0, z}

Out[41]=
{{0,11.6058,9.73763},{0,7.84251,4.92252},{
  0,0,3.12078},{10.7528,0,12.1167},{0,0,8.29897}}


Cheers,

Brian


contact at dantimatter.com wrote:
> Hello all,
>
> I have an array of the form:
>
> list={{a1,b1,c1},{a2,b2,c2}...}
>
> I'd like to get rid of elements of list based on criteria that apply to
> the a's, b's and c's separately.  For example, I'd like to keep the
> elements of list that have the following properties:
>
> m < a < n
> p < b < q
>
> I know there's an easy way to do this, but I can't figure it out.  Any
> suggestions?
> 
> Thanks!
> dan


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