On 30/09/15 12:49, waddawanna wrote:
Hello Steven,
It looks like, there is no in-built function that can do GAUSS ".*"
element-wise multiplication.
Now, if you want to make the desired computations in R, it is actually
preatty straightforward.
a<-c(1,2,3)
b<-matrix(rep(1:9,1),3,3,byrow=TRUE)
a*b
That, should work fine. But, suppose that for some reason you have following
situation, which can make you trip for hours of sleepless nights. That is,
you have a matrix "b", where number of columns equal to number of columns of
your vector "a". That is
b<-matrix(rep(1:9,1),3,3,byrow=TRUE);b
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 4 5 6
[3,] 7 8 9
a <- matrix(rep(1:3,1),1,3,byrow=TRUE)
[,1] [,2] [,3]
[1,] 1 2 3
If you try to do elementwise multilication, i.e., of those two
b*a
You get an error that they are not comfomable, that is why, you have to
write your own function (here,
I just write the for-loop):
for ( i in 1:3 ) {
foo[ ,i] = ( foo[ ,i] * bar[1,i] ) ;
}
[,1] [,2] [,3]
[1,] 1 4 9
[2,] 4 10 18
[3,] 7 16 27
I hope that this helped.
(1) You're making heavy weather by using rep() totally unnecessarily.
(2) The example you give can be done much more succinctly; for-loops
are unnecessary:
t(as.vector(a)*t(b))
(3) Please don't post to R-help via nabble (WTF ever that is). It
messes up everything.
cheers,
Rolf Turner
--
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276
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