colMeans(x, na.rm = FALSE, dims = 1)
x: array of two or more dimensions, containing numeric, complex, integer or logical values, or a numeric data frame
dims: integer: Which dimensions are regarded as ‘columns’ to sum over. It is over dimensions 1:dims.
> x <- matrix(rep(1:9),3,3) > x
[,1] [,2] [,3] [1,] 1 4 7 [2,] 2 5 8 [3,] 3 6 9
> colMeans(x)
[1] 2 5 8
Let's try a three dimensional array.
> x <- array(1:12,c(2,3,3)) > x, , 1 [,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6 , , 2 [,1] [,2] [,3] [1,] 7 9 11 [2,] 8 10 12 , , 3 [,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6 > colMeans(x,dims=1)#for dims=1, x[,1,1], x[,2,1],x[,3,1], x[,1,2] ... are columns [,1] [,2] [,3] [1,] 1.5 7.5 1.5 [2,] 3.5 9.5 3.5 [3,] 5.5 11.5 5.5 > colMeans(x,dims=2)#for dims=2, x[,,1], x[,,2],x[,,3] are columns [1] 3.5 9.5 3.5
