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

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

1 Comment

Gijs van Oort on 6 May 2013

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.

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2 Answers

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/

7 Comments

ghassan on 6 May 2013

thanks alot :-)

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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