[R] multiplying a matrix by a vector

Dimitri Liakhovitski dimitri.liakhovitski at gmail.com
Thu Nov 3 22:05:12 CET 2016


I have a matrix x and a vector y:

x <- matrix(1:6, ncol = 2)
y <- c(2,3)

I need to multiply the first column of x by 2 (y[1]) and the second
column of x by 3 (y[2]).

Of course, I could do this - but it's column by column:

x[,1] <- x[,1] * y[1]
x[,2] <- x[,2] * y[2]

Or I could repeat each element of y and multiply two matrices - that's better:

y <- rep.row(y, nrow(x))
x * y

However, maybe there is a more elegant r-like way of doing it?
Thank you!

Dimitri Liakhovitski

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