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Can someone help me with my code? Topic: integration

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LB
LB 2016-10-10
关闭： MATLAB Answer Bot 2021-8-20
Hi everyone!
I am going to calculate the integral of a function V(j). I have already found the values for V and j. I am going to use the following formulas to calculate the integral:
S(j) = S(j-1) + 1/2V(j-1)+1/2V(j) for j>=1
S(0) = 0 for j= 0
How can I write this in matlab? Hope someone can help me out here :)
  2 个评论
LB
LB 2016-10-10
Yes! And I don't know exactly how to write it to get the correct values.

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回答（2 个）

Andrei Bobrov
Andrei Bobrov 2016-10-10
编辑：Andrei Bobrov 2016-10-10
out = trapz(V);
or
out = sum(V) - sum(V([1,end]))/2;
or
S = cumtrapz(V);
or
S = [0,cumsum(sum([V(1:end-1);V(2:end)])/2)];
or
S = [0;cumsum(filter2([.5;.5],V(:),'valid'))];
Luca Fenzi
Luca Fenzi 2016-10-10
Dear LeneB, You should truncate the sum (S(j) = S(j-1) + 1/2V(j-1)+1/2V(j) for j>=1) up to N: in this way knowing V(j) for all j you can evaluate S with the following code:
N=10000; %%Truncation order of the sum
S=zeros(1,N); % Initialisation of the vector S
% S(1)=0 corresponds to S(0)=0 for j=0
% Define V(j) for j=1:N.
for i=2:N
S(i) = S(i-1) + 1/(2*V(i-1))+1/(2*V(i))
end

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