(n start with 0) An=A0+A1+ A2+A3+…+ An-1+An process??

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Baris
Baris 2013-1-16
sorry, actually the question seems easy but I am new user, ı don't know much things about MatLab functions,
how can i type that An=A0+A1+ A2+A3+…+ An-1+An in matlab mey be there is a function? n start with 0 to 100
I tried to do with A(0), A(1), .. but A(0) can not determined!!
thank you
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Jan
Jan 2013-1-17
@Baris: You cannot write "a(0)", because Matlab starts indices at 1. Simply write "a(1)", which has no influence to the result.
Baris
Baris 2013-1-21
thank you for helping. actually it is easy to implement if I use a(1) in stead of a(0).I just wanted to learn that. So,ıf there is no way to do, I will do using a(1).
thank you so much again!!

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回答（4 个）

Ryan Livingston
Ryan Livingston 2013-1-16
In MATLAB, array indices begin at 1 rather than zero so A(0) generally won't succeed.
The SUM function could be of assistance:
http://www.mathworks.com/help/matlab/ref/sum.html
Matt J
Matt J 2013-1-16
Use the CUMSUM command, e.g.
>> cumsum([4 6 9 3])
ans =
4 10 19 22
Azzi Abdelmalek
Azzi Abdelmalek 2013-1-16
An=@(n) cos(n) % example for cos(n)
out=sum(arrayfun(@(x) An(x),0:n))
Image Analyst
Image Analyst 2013-1-16
Not sure if this is what you meant, but the code below will do EXACTLY what you said. This code will replace the nth element only, with the sum of the elements from 1 to n, and leave the other elements of A unchanged. n is 100. If that's not what you meant, then please be specific.
% Define sample data of length 120.
A = randi(9, 1, 120)
n = 100; % or whatever element you want to stop at.
fprintf('A(%d) initially equals %d\n', n, A(n));
% Replace the nth element only, with the sum of the elements from 1 to n.
% Leave the other elements of A unchanged!
A(n) = sum(A(1:n))
fprintf('but now A(%d) equals %d\n', n, A(n));
Note: because MATLAB starts at 1 but you started at 0, you may have to adjust n or else adjust the sum:
A(n) = sum(A(1:n+1)); % n=8 is the 9th element if you consider A starting at 0

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