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Re: Comparing Corresponding Columns of Two Matrices

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97547] Re: [mg97496] Comparing Corresponding Columns of Two Matrices
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Sat, 14 Mar 2009 18:18:30 -0500 (EST)
  • References: <200903141039.FAA12977@smc.vnet.net>
  • Reply-to: drmajorbob at bigfoot.com

If I understand the problem correctly, then... in order of increasing  
speed or simplicity (I think):

x = RandomInteger[{0, 3}, {10, 4}]
y = RandomInteger[{0, 3}, {10, 4}]

{{3, 3, 0, 3}, {3, 1, 2, 3}, {1, 2, 1, 1}, {0, 1, 3, 1}, {1, 2, 1,
   2}, {0, 2, 3, 2}, {0, 1, 0, 3}, {0, 3, 1, 1}, {0, 0, 1, 1}, {0, 0,
   3, 2}}

{{0, 0, 3, 3}, {2, 1, 1, 1}, {1, 3, 2, 2}, {3, 1, 1, 3}, {0, 0, 2,
   0}, {2, 1, 0, 2}, {2, 3, 3, 2}, {0, 0, 2, 1}, {3, 1, 2, 2}, {3, 3,
   1, 1}}

Map[Boole, Thread /@ Thread[Transpose@x > Transpose@y], {2}]

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

or

Map[Boole, Positive /@ (Transpose@x - Transpose@y), {2}]

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

or

f[a_] = Boole@Positive@a;
SetAttributes[f, Listable]
f /@ (Transpose@x - Transpose@y)

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

or

f[a_] = Boole@Positive@a;
SetAttributes[f, Listable]
f /@ Transpose[x - y]

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

or

Clear[f]
f[a_, b_] := Boole@Positive[a - b];
SetAttributes[f, Listable]
f[Transpose@x, Transpose@y]

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

or

Clear[f]
f[a_, b_] := Boole@Positive[a - b];
SetAttributes[f, Listable]
Transpose@f[x, y]

{{1, 1, 0, 0, 1, 0, 0, 0, 0, 0}, {1, 0, 0, 0, 1, 1, 0, 1, 0, 0}, {0,
   1, 0, 1, 0, 1, 0, 0, 0, 1}, {0, 1, 0, 0, 1, 0, 1, 0, 0, 1}}

Bobby

On Sat, 14 Mar 2009 05:39:39 -0500, Gregory Lypny  
<gregory.lypny at videotron.ca> 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
>



-- 
DrMajorBob at bigfoot.com


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