Re: Comparing Corresponding Columns of Two Matrices

*To*: mathgroup at smc.vnet.net*Subject*: [mg97555] Re: Comparing Corresponding Columns of Two Matrices*From*: Raffy <raffy at mac.com>*Date*: Sun, 15 Mar 2009 05:27:42 -0500 (EST)*References*: <gpg1gu$cl7$1@smc.vnet.net>

On Mar 14, 3:39 am, Gregory Lypny <gregory.ly... 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 X = RandomReal[{0, 1}, {100, 4}]; Y = RandomReal[{0, 1}, {100, 4}]; r1 = Boole@MapThread[Greater, {X, Y}, ArrayDepth[X]]; Or, even better: r2 = Clip[X - Y, {0, 0}, {0, 1}];