![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/274639/image.png)
Double sum with upper limits
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Hi
I am trying to do the following calululation in matlab:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/274632/image.png)
But I do not how how to do the two sums in the front. Our data (d) is a 67x120 array.
Any suggestions would be appreciated :)
2 Comments
Accepted Answer
Guillaume
on 2 Mar 2020
Edited: Guillaume
on 2 Mar 2020
s = (1:size(d, 1)).';
result = sum(sum(d .* cos(s))) / sum(cos(s));
Loops not needed, they're just a waste of time.
3 Comments
Guillaume
on 2 Mar 2020
Yes, I made a mistake, there was a sum missing in the denominator. I assumed that the
could be taken out of the double sum, i.e. it's over the whole range. It's not clear and we didn't get an answer to Darova's question. So, my code implement:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/274701/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/274702/image.png)
If it's a partial sum as you think, then:
s = (1:size(d, 1)).';
result = sum(sum(d .* cos(s) ./ cumsum(cos(s))));
which implements
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/274703/image.png)
More Answers (1)
Luna
on 2 Mar 2020
Maybe something like that would help:
d = rand(67,120);
sum_of_cos_s = 0;
result = 0;
for s = 1:67
for j = 1:120
sum_of_cos_s = sum_of_cos_s+cos(s);
result = result + (d(s,j)*cos(s))/sum_of_cos_s;
end
end
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