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Re: Comparing Corresponding Columns of Two Matrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97534] Re: Comparing Corresponding Columns of Two Matrices
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 14 Mar 2009 18:16:08 -0500 (EST)
  • References: <gpg1gu$cl7$1@smc.vnet.net>

Hi,

\[ScriptCapitalX] = Table[RandomInteger[{0, 255}], {10}, {4}];
\[ScriptCapitalY] = Table[RandomInteger[{0, 255}], {10}, {4}];


MapThread[#1 > #2 &, {\[ScriptCapitalX], \[ScriptCapitalY]}, 2]

??

Regards
   Jens

Gregory Lypny wrote:
> Hello everyone,
> 
> I'm trying to develop a modest skill in mapping functions and I've  
> been working on this problem.
> 
> Suppose I have two 100 x 4 matrices, X and Y, and I want to see  
> whether each value in a column of X is bigger than each value in the  
> corresponding column of Y.  In other words, compare column 1 of X with  
> column 1 of Y, column 2 of X with column 2 of Y, and so on.
> 
> It's easy to generate a 100 x 4 table of Booleans using Table as
> 
> 	Table[Boole[X[[i ,  j]] > Y[[i, j]]], {i, 100}, {j, 4}]
> 
> But what about without Table?  I am able to do it for the comparison  
> of any one column as
> 
> 	Boole[#[[1]] > #[[2]]] & /@ Transpose[{X[[All, ]], Y[[All, 1]]}]
> 
> but I'm not sure how to extend this to other columns.  Any tip would  
> be much appreciated.
> 
> Regards,
> 
> 	Gregory
> 


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