Section: Elementary Functions
y = std(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 variance.  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.
std
function
--> A = [5,1,3;3,2,1;0,3,1] A = 5 1 3 3 2 1 0 3 1
We start by calling std without a dimension argument, in which 
case it defaults to the first nonsingular dimension (in this case, 
along the columns or d = 1).
--> std(A)
ans = 
    2.5166    1.0000    1.1547 
Next, we take the variance along the rows.
--> std(A,2)
ans = 
    2.0000 
    1.0000 
    1.5275