[R] multiplying a matrix by a vector

[Dimitri Liakhovitski]

I love R for it: if you experiment enough with t() you can find a way
to multiply almost anything by almost anything!
:)

On Thu, Nov 3, 2016 at 5:32 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> Hello,
>
> Take advantage that in R '*' recycles its arguments (the shorter one) and
> that the operation is performed column-wise:
>
> t(y * t(x))
>
> Hope this helps,
>
> Rui Barradas
>
>
> Em 03-11-2016 21:05, Dimitri Liakhovitski escreveu:
>>
>> Hello!
>>
>> 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]
>> x
>>
>> Or I could repeat each element of y and multiply two matrices - that's
>> better:
>>
>> rep.row<-function(x,n){
>>    matrix(rep(x,each=n),nrow=n)
>> }
>> 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