Double sum with upper limits

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H Lange
H Lange el 2 de Mzo. de 2020
Comentada: Luna el 3 de Mzo. de 2020
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 comentarios
darova
darova el 2 de Mzo. de 2020
Luna
Luna el 2 de Mzo. de 2020
Editada: Luna el 2 de Mzo. de 2020
What have you done so far as coding? And what is d?

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Respuesta aceptada

Guillaume
Guillaume el 2 de Mzo. de 2020
Editada: Guillaume el 2 de Mzo. de 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 comentarios
Guillaume
Guillaume el 2 de Mzo. de 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:
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
Luna el 3 de Mzo. de 2020
You are right.

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Más respuestas (1)

Luna
Luna el 2 de Mzo. de 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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