# [R] Equivalent to matlab ".*" operator in R

John C Frain frainj at gmail.com
Wed Nov 19 22:48:13 CET 2014

```What you have written does not work in Matlab -

>> y = [0 0;0.5 0.5;1 1]

y =

0         0
0.5000    0.5000
1.0000    1.0000

>> z = [12, -6]

z =

12    -6

.

>> y .* z
Error using  .*
Matrix dimensions must agree.

When dimensions agree it you get the same result in R as in Matlab by using
the * operator

> y = matrix(cbind(c(0, 0.5, 1),c(0, 0.5, 1)),ncol=2)
> y
[,1] [,2]
[1,]  0.0  0.0
[2,]  0.5  0.5
[3,]  1.0  1.0
> z = matrix(1:6, ncol=2)
> z
[,1] [,2]
[1,]    1    4
[2,]    2    5
[3,]    3    6

> prod <- matrix(y*z,2)
> prod
[,1] [,2] [,3]
[1,]    0    3  2.5
[2,]    1    0  6.0
> prod <- matrix(y*z)
> prod
[,1] [,2]
[1,]    0  0.0
[2,]    1  2.5
[3,]    3  6.0
>

John C Frain
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Dublin 14
Ireland
www.tcd.ie/Economics/staff/frainj/home.html
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On 19 November 2014 16:48, Boris Steipe <boris.steipe at utoronto.ca> wrote:

> Or ... if you mean "simpler" as in "less to type", you can define your own
> binary operator by enclosing it in "%" signs, and the assign any of the
> previously proposed solutions, e.g.
>
> y = matrix(cbind(c(0, 0.5, 1),c(0, 0.5, 1)),ncol=2)
> z = matrix(c(12, -6),ncol=2)
> '%.*%' <- function(a,b) {a * rep(b, each=3)}
>
>
> y %.*% z
>
>
>      [,1] [,2]
> [1,]    0    0
> [2,]    6   -3
> [3,]   12   -6
>
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