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MathGroup Archive 2006

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Re: Selecting Many Things Rather Than Selecting One Thing From Many

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66210] Re: Selecting Many Things Rather Than Selecting One Thing From Many
  • From: "Chris Chiasson" <chris.chiasson at gmail.com>
  • Date: Thu, 4 May 2006 05:20:39 -0400 (EDT)
  • References: <e39k7e$cno$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Select and Cases are very similar. I would recommend Cases for this.
The code below gives results in a form similar to the one MathGroup
showed you last time.

In[1]:=
dim=12;

In[2]:=
maxint=200;

In[7]:=
theMatrix=Table[Random[Integer,maxint],{dim},{dim}];

In[4]:=
K=Extract[theMatrix,
    Table[{Random[Integer,{1,dim}],Random[Integer,{1,dim}]},{4}]]

Out[4]=
{46,54,171,17}

In[5]:=
Select[#1,#>maxint/2&]&/@Transpose[theMatrix]

Out[5]=
{{136,195,121,169,178,118,122},{195,190,106,149,171},{128,132,
  135,168,195},{175,153,116,134,110,

122,193,174,173,166},{181,173,129,136},{192,135,150,141,136,191,130,101,
    119},{105,161,152,102,195,188,174,102},{102,171,154,117,
    155,114,132},{109,152,129,168,189,197,133,162},{122,123,145,128,

158,150},{107,190,106,121,169,123,177,194},{177,115,106,119,123,120,132}}

In[6]:=
Cases[#1,Alternatives@@K]&/@Transpose[theMatrix]

Out[6]=
{{},{46,54,171},{},{17},{},{46},{},{171},{},{46},{},{}}


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