sum
sum of the elements of an array along a specified dimension.
(y)=sum(x)
(y)=sum(x, dim)
 Inputs x Any numeric array. dim A positive integer not greater than the number of dimensions of x . Outputs y The array of sum of the elements of x along the dimension dim whose default value is 1 .

Description
If x is a vector, the output is the sum of all the elements of the vector. Otherwise the output is of the same size as the input except that along the dimension dim the size of the output is 1 . The element y[i,j,k,...1, p, q,..] (with 1 corresponding to the dimension dim ) of the output is the sum of the elements of the vector x[i,j,k,....,:,p,q,...] where i, j, k, ...,p,q,... are scalar integers ranging through the size of the input along the corresponding dimension.
Example
>>a=floor(randn(3,4,2)*100)
>>a
[:,1:4, 1]
-125          -21          -32          -30
-29          166          -12          -69
-22          -38           24          105
[:,1:4, 2]
93           45         -187           48
-108          -63          -63            3
26          144         -137           69

>>sum(a)
[:,1:4, 1]
-176          107          -20            6
[:,1:4, 2]
11          126         -387          120

>>sum(a,3)
[:,1:4, 1]
-32           24         -219           18
-137          103          -75          -66
4          106         -113          174