[R] "adding" matrix of smaller dimensions to matrix of larger dimensions and "apply" question
Rainer M Krug
Rainer+R-help at krugs.de
Tue Oct 23 17:03:58 CEST 2007
Hi
I have another question concerning matrices:
I have two matrices:
> b <- matrix(1:25,5,5,byrow=T)
> b
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2 3 4 5
[2,] 6 7 8 9 10
[3,] 11 12 13 14 15
[4,] 16 17 18 19 20
[5,] 21 22 23 24 25
and
> d <- matrix(1:4,2,2,byrow=T)
> d
[,1] [,2]
[1,] 1 2
[2,] 3 4
>
and I want to "add" d to b in such a way that I specify one cell in
matrix b , e.g. [1,2]:
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2+1 3+2 4 5
[2,] 6 7+3 8+4 9 10
[3,] 11 12 13 14 15
[4,] 16 17 18 19 20
[5,] 21 22 23 24 25
Is there an easy way of doing this, apart from iterating through the
matrix d?
Also, when I use
> apply(d, c(1,2), function(x) {})
is there a way of knowing the column anr row which the element x is
from, or o I have to use for loops for that?
Thanks in advance,
Rainer
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