# Why can't Matlab calculate a(0)

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Michael Bernard on 4 Feb 2013
Hi everyone, its not serious problem at all. But I just want to know. Why cant Matlab calculate a(0) in a for loop.
Example: n=3;L=4;
>> ai=[2 4 6 8];
for m=0:n
an(m)=-ai(L-m)/ai(1)
end
Matlab will give an error message that says
"Attempted to access (0); index must be a positive integer or
logical."
My question is why?? I get results if I use
for m=1:n
an(m)=-ai(L-m)/ai(1)
end
because a(1) , a(2) etc can be found in matlab. so why not a(0)???

Azzi Abdelmalek on 4 Feb 2013
Edited: Azzi Abdelmalek on 4 Feb 2013
It's just how Matlab works, allows only positive integer or logical index. You can resolve the problem, for example
for k=0:10
y(k+1)=sin(k)
end
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Michael Bernard on 4 Feb 2013
Thanks a lot Azzi Abdelmalek .Its well understood

### More Answers (1)

Walter Roberson on 4 Feb 2013
You need to distinguish between array notation and function notation.
Array notation requires that the arguments describe integer array locations. Array locations in MATLAB are numbered starting from 1, as is the case for Fortran and a number of other computer languages (but not all -- e.g., C numbers starting from 0.)
function notation is what is used when you say things like
f(1.37) = 8.2
or
an(0) = 4
That notation is completely valid in mathematics, but it has no equivalent in MATLAB, except inside MuPAD (the symbolic toolbox).