Asked by ghassan
on 6 May 2013

hi, i'm using m file in cell mode to solve f(x)=sin (x), where x = 0.8 and i'm getting "??? Subscript indices must either be real positive integers or logicals. " error how it can be solved

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Answer by John Doe
on 6 May 2013

Edited by John Doe
on 6 May 2013

Is this what you're trying to do?

%% Don't run this part A = magic(4);

%% Run this part by itself x = 0.8; f = sin(x)

%% Not this part A = rand(4);

What you do is: Place your cursor in the middle section. Then press Ctrl + Enter.

Please watch this video:

http://blogs.mathworks.com/videos/2011/07/26/starting-in-matlab-cell-mode-scripts/

Show 4 older comments

ghassan
on 6 May 2013

%% x= 0.8; f = x^2 ; exact = 2*x; for k=1:10; h(k)=10^-k; end for k=1:10; fapp(x)=((x+h(k)^2)-x^2)/h(k); end fapp error = abs (exact-fapp)

im trying to use this code in cell mode and the following error appears

??? Subscript indices must either be real positive integers or logicals.

Jan Simon
on 6 May 2013

Please, ghassan, format your code properly. Follow the "? Help" link to learn how to use the forum's interface. Thanks.

It would be helpful, if you post the complete error message and explain, in which line the problem occurres. Then we do not have to guess the details.

It is more complicated to answer to information, which is provided in the comment section. Please collect all required information in the original question, for this reason editing the questions has been introduced in this forum.

Answer by Jan Simon
on 6 May 2013

Concerning the comment http://www.mathworks.com/matlabcentral/answers/74763#comment_147582

fapp(x) = ...

No, you cannot use x=0.8 as index. Do you want `fapp(k)`?

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## 1 Comment

## Gijs van Oort (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/74763#comment_147545

Please tell us the exact code you're using. Is it actually Matlab code? The code you're giving ('solve f(x)=sin(x)' ) is not Matlab compatible.