Re: Fast matrices comparison

• To: mathgroup at smc.vnet.net
• Subject: [mg115922] Re: Fast matrices comparison
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Wed, 26 Jan 2011 05:04:04 -0500 (EST)

```m1 = {{8, 7}, {3, 9}};
m2 = {{2, 3}, {4, 5}};

m1 = m1 Boole@Positive[m1 - m2]

{{8, 7}, {0, 9}}

Bobby

On Tue, 25 Jan 2011 03:19:23 -0600, JJ <wateronwildfire at gmail.com> wrote:

> Hi MathGroup
>
> I have to compare two big matrices (in the SparseArray form), say m1 and
> m2.
> I need that the elements of m1 will be replaced by 0 if they are less or
> equal to
> the corresponding elements of m2.
>
> For example, if m1={{8,7},{3,9}} and m2={{2,3},{4,5}},
> I would like to have m1={{8,7},{0,9}} because m1[[2,1]]<m2[[2,1]].
>
> I can do it easily with two nested for loops but I think it is not an
> efficient way to do it.
> I was wondering if somebody knows how to do it using a fast conditional
> replacement rule and/or pure functions.
>
> Thank you.
>
>

--
DrMajorBob at yahoo.com

```

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