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rmatrixmatrix-multiplicationmultiplication

Multiplication of matrix in R

I have the following problem :

w <- matrix(1:3,nrow=3,ncol=1)

mymat <- as.matrix(cbind(a = 6:15, b = 16:25, c= 26:35))

mymat

      a  b  c
 [1,]  6 16 26
 [2,]  7 17 27
 [3,]  8 18 28
 [4,]  9 19 29
 [5,] 10 20 30
 [6,] 11 21 31
 [7,] 12 22 32
 [8,] 13 23 33
 [9,] 14 24 34
[10,] 15 25 35

I want to obtain the following results in a matrix the same size as mymat:

       a  b  c
 [1,]  6*1 16*2 26*3
 [2,]  7*1 17*2 27*3
 [3,]  8*1 18*2 28*3
 ...

I've tried the lappy function but I am unable to get the results I want. Thanks!

Solution

  • Using sweep():

    sweep(mymat, 2, w, "*")

    Converting w into a matrix of the same dimensions:

    mymat * t(w)[rep(1, NROW(mymat)), ]