| MATLAB Function Reference | |
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
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