MATLAB Function Reference

sum

Sum of array elements

Syntax

• B = sum(A)
  B = sum(A,dim)
  

Description

B = sum(A) returns sums along different dimensions of an array.

If A is a vector, sum(A) returns the sum of the elements.

If A is a matrix, sum(A) treats the columns of A as vectors, returning a row vector of the sums of each column.

If A is a multidimensional array, sum(A) treats the values along the first non-singleton dimension as vectors, returning an array of row vectors.

B = sum(A,dim) sums along the dimension of A specified by scalar dim.

Remarks

sum(diag(X)) is the trace of X.

Examples

The magic square of order 3 is

• M = magic(3) 
  M = 
       8    1    6
       3    5    7
       4    9    2
  

This is called a magic square because the sums of the elements in each column are the same.

• sum(M) =
       15    15    15
  

as are the sums of the elements in each row, obtained by transposing:

• sum(M') = 
       15    15    15
  

See Also

cumsum, diff, prod, trace

subvolume

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