How to apply vector value function to a multidimensional array indexed by the remaining dimensions?

x <- array(1:100,c(3,4,5))

y <- apply(x, MARGIN=c(2,3), FUN=sum)
y

z <- matrix(0, nrow=4, ncol=5);
for (ii in 1:3) z <- z + x[ii,,];
z

stopifnot(all.equal(z,y))

Hi,
?I am looking for some generalization of colSums and rowSums for general
vector valued functions, and for arrays of more than 2 dimensions.
?So as a concrete example, suppose I have a 3 dimensional array, given by x
= array(1:100,c(3,4,5)).
and I want to sum the 3rd index of x to obain a 3 by 4 matrix. Using rowSums
would return a vector of length 3 because it treats the last two indices as
a single index.

?Besides summation, let's say if I define a vector valued function
f<-function(x){min(x[1],min(x[2],x[3]))}, and I want to apply f to the last
index of x, meaning for each 1<= i <= 3, 1<=j <=4, I want to compute
f(x[i,j,]), and then put them in a 3 by 4 matrix. How would I be able to do
that without using a for loop?

?thanks.

?Sincerely,
?John
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