MEAN MEAN Mean Function Usage Computes the mean of an array along a given dimension. The general syntax for its use is y = mean(x,d) where x is an n-dimensions array of numerical type. The output is of the same numerical type as the input. The argument d is optional, and denotes the dimension along which to take the mean. The output y is the same size as x, except that it is singular along the mean direction. So, for example, if x is a 3 x 3 x 4 array, and we compute the mean along dimension d=2, then the output is of size 3 x 1 x 4.