CUMSUM Cumulative Summation Function

Section: Elementary Functions

Usage

Computes the cumulative sum of an n-dimensional array along a given dimension. The general syntax for its use is 
  y = cumsum(x,d)

where x is a multidimensional array of numerical type, and d is the dimension along which to perform the cumulative sum. The output y is the same size of x. Integer types are promoted to int32. If the dimension d is not specified, then the cumulative sum is applied along the first non-singular dimension.

Function Internals

The output is computed via

Example

The default action is to perform the cumulative sum along the first non-singular dimension. 
--> A = [5,1,3;3,2,1;0,3,1]

A = 
 5 1 3 
 3 2 1 
 0 3 1 

--> cumsum(A)

ans = 
 5 1 3 
 8 3 4 
 8 6 5

To compute the cumulative sum along the columns: 

--> cumsum(A,2)

ans = 
 5 6 9 
 3 5 6 
 0 3 4

The cumulative sum also works along arbitrary dimensions 

--> B(:,:,1) = [5,2;8,9];
--> B(:,:,2) = [1,0;3,0]

B = 

(:,:,1) = 
 5 2 
 8 9 

(:,:,2) = 
 1 0 
 3 0 

--> cumsum(B,3)

ans = 

(:,:,1) = 
  5  2 
  8  9 

(:,:,2) = 
  6  2 
 11  9