Double sum with upper limits
显示 更早的评论
Hi
I am trying to do the following calululation in matlab:
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 个评论
darova
2020-3-2
采纳的回答
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 个评论
My understanding of /Sigma[cos(s)] part, it should be divided into sum of cos(s) from 1 to what s is until that iteration. For example if s is 20 while j = 3;
d(20,3)*cos(20) / ( cos(1)+cos(2)+...+cos(20) )
so your result gives a vector (1x67). I assume that result must be a scalar.
Guillaume
2020-3-2
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:
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:
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
Luna
2020-3-3
You are right.
更多回答（1 个）
Luna
2020-3-2
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
类别
在 帮助中心 和 File Exchange 中查找有关 Logical 的更多信息
产品
Translated by 
