R>oop*drop(oo)
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 8 10 12
[3,] 21 24 27
R fastest way to multiply rows of a matrix by rows of a vector
문제
I want to multiply rows of a matrix by EACH row (element) of a vector, not the entire vector (as the other question already posted talks about.)
for example, I want to use these two matrices (or oo is a vector, since it's one column)
oo=matrix(1:3,3,1)
oop=matrix(1:9,3,3,byrow=TRUE)
to output
1 2 3
8 10 12
21 24 27
I need to do this VERY efficiently, as I need to do it with massive amounts of data thousands of times. I used
diag(as.vector(oo))%*%oop
but this is much too slow.
해결책
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