Matrix multiplication causes "non-conformable" error when called from `optim`-CodePudding

i am trying to run a simple optimization problem and i always get the 'non-conformable arguments' error. However the error occurs only within optim, so i am at the end of my understanding. Here is my code:

f <- function(W, x, y){
  temp <- W %*% x
  temp1 <- t(temp) %*% temp
  temp2 <- t(temp) %*% y
  temp3 <- t(y) %*% y
  (temp1 - 2 * temp2   temp3)[1]
}

x <- matrix(c(1,2), ncol=1)
y <- matrix(c(5,3), ncol=1)
W <- matrix(c(1,2,3,4), ncol=2)
f(W,x=x,y=y)
> 53

so far so good. The function works just fine. However once i put the values into optim:

optim(par=W, fn=f, x=x, y=y)

i get:

> Error in W %*% x : non-conformable arguments

how can i fix this?

CodePudding user response：

If you add print(W) at start of f you would see that W is used as vector (it seems that optim converts par to vector). You should transform W to matrix with adequate dimensions at start of f.