Automatic multiplication between vector and matrix

Question

I have this R code:

> coef
[1] 1.5 2.4 3.9 4.4
> y
     [,1] [,2] [,3] [,4]
[1,]    1    2   12   45
[2,]    5    6    7    8
[3,]    9   10    2   12
         


        

Answer 1

A late entry:

coef[col(y)]*y

On my system, this is the fastest.

                                      test replications elapsed relative
6                         coef[col(y)] * y        10000   0.068    1.000
5 scale(y, center = FALSE, scale = 1/coef)        10000   0.640    9.412
4                   sweep(y, 2, coef, "*")        10000   0.535    7.868
3                t(apply(y, 1, "*", coef))        10000   0.837   12.309
1                           t(t(y) * coef)        10000   0.176    2.588
2                         y %*% diag(coef)        10000   0.187    2.750