R中3D数组列表的平均值

Question

How can I calculate the means of arrays stored in a list in R? The result should be an array of the same size containing the means... For example:

a1 <- array(runif(100), dim=c(4, 5, 5))
a2 <- array(runif(100), dim=c(4, 5, 5))
a3 <- array(runif(100), dim=c(4, 5, 5))
a4 <- array(runif(100), dim=c(4, 5, 5))
a5 <- array(runif(100), dim=c(4, 5, 5))

l <- list(a1, a2, a3, a4, a5)

[...]

should result in an array of dimension 4, 5, 5 containing the means.

I can do it for a list of matrices with:

apply(simplify2array(myList), 1:2, mean)

but it doesn't work for my purpose...

Thanks for any clue!

Answer 1

也许我们可以使用Reduce

Reduce(`+`, l)/length(l)

Answer 2

You could first transform you list of arrays into a 4D array and then use apply :

a <- array(unlist(l), dim = c(dim(l[[1]]), length(l)))
apply(a, 1:3, mean)