Asked by Omidreza Ghafarinejad
on 22 Feb 2015

hi everybody. i want to calculate the sum of a serie that has a function which has two variables named 'xi' and 'eta'. 'xi' and 'eta' are the coordinates of 4 points. for example i want to calculate the sum of the serie from point 1 to point 4 and in each point 'xi' and 'eta' has a specific value. can anyone help me how to write the code??

Answer by dpb
on 22 Feb 2015

xi=[list of four values];

eta=[list of four more presumably different values];

func=yourfunction(xi,eta); % compute the function

sumFunc=cumsum(func);

Omidreza Ghafarinejad
on 22 Feb 2015

thanks but it didn't work.

dpb
on 22 Feb 2015

How do we Know that? You didn't show any more of your work than your original question... :(

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Answer by Shoaibur Rahman
on 22 Feb 2015

% xi eta

x =[1 2;...

3 4;...

4 5;...

6 7];

y = sum(x) % only sum of all elements along each column

y = cumsum(x) % cumulative sum along each column

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Answer by Image Analyst
on 22 Feb 2015

Be more specific. Why can't you give us the series? Is it homework or something? If you don't get more specific then you'll just get more answers like dpb's (which is all your fault rather than dpb's because you were not specific enough to be able to answer your question).

What's wrong with using the sum() function, or even a brute force for loop()?

Omidreza Ghafarinejad
on 22 Feb 2015

Image Analyst
on 22 Feb 2015

If you want to sum a 3D matrix "j" between certain rows and columns, do this

subArray = j(row1:row2, col1:col2, :);

theSum = sum(subArray(:));

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Answer by Omidreza Ghafarinejad
on 24 Feb 2015

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