Index in position 2 exceed array bounds

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Maureen Domtche 2019-4-11

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评论： Bob Thompson 2019-4-12

Here's my code and im tryna figure out why i always get "index in position 2 exceed arra bounds"

What do i have to change?

function [t, y] = Euler_implicite(fonction, J ,t0,y0, h,e, Nt)

y(1,:) = y0;

t=zeros(Nt);

t(1) = t0;

for i = 1:Nt

g= y(:,i+1)-y(:,i)- h*fonction;

t(i+1)=t(i)+h;

y = newton_systeme(g,J,SP, niteration, precision);

end

newton_systeme(g,J,y0,e,Nt);

end

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Adam Danz 2019-4-11

What about Nt (and e)?

Maureen Domtche 2019-4-11

Nt = 200 e = 0.05

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回答（2 个）

Adam Danz 2019-4-11

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编辑：Adam Danz 2019-4-11

在 MATLAB Online 中打开

Just before the i-loop, you set y equal to 10.

%from your code...
y0 = 10; 
y(1,:) = y0;  % same as y = 10

Then on the first iteration of the i-loop, i=1 so when you execute this line

g= y(:,i+1)-y(:,i)- h*fonction;
% ----------

you're trying to access the second value of y but y only has 1 value (y=10)!

Even if that didn't cause an error this section below would (also) cause an error.

g= y(:,i+1)-y(:,i)- h*fonction;
%                   -----------
K>> h*fonction
Undefined operator '*' for input arguments of type 'cell'. 

So there's at least a couple areas of your code you need to re-think. In other words, your errors are conceptual errors. Your code isn't written properly and that's something you'll need to work on in the context of your project.

I suggest going through your code line-by-line to confirm that it's doing what it's supposed to be doing.

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Adam Danz 2019-4-11

We don't have enough information to fix it (or confirm that it's broken). It's just a bunch of letters to us.

Bob Thompson 2019-4-12

What you need to do to fix your code is to figure out how to get more than one element in y. As has been mentioned already the calculation of g is looking for two elements of y when only one exists. We are not particularly able to help you fix this particular problem because it is a very contextual solution, not something to do with the code. All we can tell you is that this is why the code isn't working.

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