How to apply for loop in case of product of function inside double summation?

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chaaru datta
chaaru datta 2024-2-1
移动：Dyuman Joshi 2024-2-15
Hello all, I am trying to code the following double summation that involves product inside it in MATLAB.
----(1)
I had tried the following code :
pr = 0;
for i = 0:1
for j = 0 : 1
pr_1 = a(i)*b(j);
pr = pr+pr_1;
end
end
P = 1-pr;
My query is that is the above code correctly representing equation (1).
Any help in this regard will be highly appreciated.
  2 个评论
Dyuman Joshi
Dyuman Joshi 2024-2-1
移动：Dyuman Joshi 2024-2-15
That is simply the sum of product of pairs in the given index range for a and b, thus P can be defined like this -
P = 1-sum((a(1:2).')*b(1:2),'all')
Keep in mind that indexing in MATLAB starts from 1.
VBBV
VBBV 2024-2-1
Though you may not need double for loop as @Dyuman Joshi demonstrated, you can modify your present code as shonn in my answer which i believe is your question about. .

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回答（2 个）

VBBV
VBBV 2024-2-1
编辑：VBBV 2024-2-1
R = 0:1;
a = 1:10; b = -10:10;% define values
for i = 1:length(R)
for j = 1:length(R)
pr_1(i,j) = a(i)*b(j);
end
pr(i) = sum(pr_1(i,:));
end
P = 1-sum(pr)
You can modify the existing code as above
  5 个评论
显示 3更早的评论
Torsten
Torsten 2024-2-1
Use
pr_1 = a(i+1)*b(j+1);
instead of
pr_1 = a(i)*b(j);
in your code.
Array indexing in MATLAB starts with 1, not with 0.

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Matt J
Matt J 2024-2-2
编辑：Matt J 2024-2-2
The most efficient approach, especially as a and b become longer, is to separate the sums, leading to a one-line computation:
P=1-sum(a)*sum(b);
Even if this is intended to be an exercise in writing loops, it would make more sense to write separate loops for sum(a) and sum(b).

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