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# Error in a matlab function

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Elena on 15 Jan 2015
Closed: MATLAB Answer Bot on 20 Aug 2021
Hello. i have a problem of dimension in this function:
function Generalized_coefficient= loggfc(alpha,n)
for m=1:1:n-1
f=[2:1:m-1];
g=[1:1:m-1];
x=[1:1:m+1];
Generalized_coefficient =logalpha;
a= log(m-alpha*f)+ Generalized_coefficient(f);
b=logalpha +Generalized_coefficient(g);
themax= max(a,b);
x(1)=log(m-alpha*1)+ Generalized_coefficient(1);
x(f)=themax+ log(exp(a-themax)+ exp(b-themax));
x(m+1)=logalpha+ Generalized_coefficient(m);
Generalized_coefficient=x;
end
end
When i put n=2; it's ok but when i set n=3 matlab provide me this error
"Attempted to access Generalized_coefficient(2); index out of bounds because numel(Generalized_coefficient)=1" How can i correct the code? Thank you
dpb on 15 Jan 2015
You can't "modify" numel; it's the size of the array in the argument. Only changing that size/length of the array to be as long as the largest index or restricting the address to be within the actual length will cure the problem.
The difficulty is as described that it's not at all clear what your function is supposed to be doing since all we have is nonworking code; no description of what an expected output would be given an input.

Image Analyst on 15 Jan 2015
"logalpha" is not defined. Perhaps you meant log(alpha).
Then, for n=2, m goes from 1 to 1, you say
f=[2:1:0]; % This will be empty.
a= log(m-alpha*f)+ Generalized_coefficient(f); % Kaboom!
so that will bomb - not sure why you said it doesn't.
Then, for n=2, m goes from 1 to 2, you say
f=[2:1:2]; % This will be 2.
a= log(m-alpha*f)+ Generalized_coefficient(f); % Kaboom!
Well, Generalized_coefficient does not have two elements yet. Luckily there is a way to solve this, and here it is.