summation

how to implement summation in matlab Is there any function for 2D summation in matlab

Answer 1

[TAB]

A=rand(5);
As=sum(sum(A));

[Jan]

SUM(SUM(A)) is slower than SUM(A(:) on older Matlab versions (I assume <= 2009a), and on single core machines. On a modern system SUM(SUM(A)) is parallelized and faster in consequence.

[Andrei Bobrov]

Hi Jan!

A= rand(5000);

tic,sum(sum(A));toc

tic,sum(A(:));toc

clear A

Elapsed time is 0.037663 seconds.

Elapsed time is 0.037902 seconds.

MATLAB R2010a, Intel Core2 Duo, 2.13 GHz, 2 GB RAM

[TAB]

On Matlab R2007a , C2D, 4GB RAM

A= rand(5000);

tic,sum(sum(A));toc --> 0.047444 Sec

tic,sum(A(:));toc --> 0.047441 Sec

Yes, Andrei's version is faster. :-)

Answer 2

[Andrei Bobrov]

sum(A(:)) % A - double array 2d