How to solve Attempted to access (0) error.?

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Nimisha
Nimisha le 22 Nov 2014
Réponse apportée : Jan le 23 Nov 2014
In attached figure, one equation is there which i need to implement.
where,
x[n] = a* r^n
a = 11; r = 0.9; L = 19; 0<=m<=L; 0<=n<=L
for this i have written a script.
clear all
a = 11;
r = 0.9;
L = 19;
for m = 0:L
for n = 0:L
S(m) = a*(r^n);
end
end
plot(S,m)
xlabel('Value of "S"');
ylabel('Value of "L"');
title('a = 11; r = 0.9; L = 19')
When i run it, it gives following error
Attempted to access (0); index must be a positive integer or logical.
Error in Question_6 (line 8)
S(m) = a*(r^n);
How to solve it..?

Réponse acceptée

Geoff Hayes
Geoff Hayes le 23 Nov 2014
Nimisha - unlike C/C++, indexing into MATLAB arrays begins at one instead of zero. Since your code is iterating (over m) from 0 to L, then the error message makes sense for
S(m) = a*(r^n);
I don't think that you have quite gotten this equation correct. From your attached image, it looks like
S[m] = sum(n=0...m)x[n];
which to me means that your S could be initialized as
a = 11;
r = 0.9;
L = 19;
S = zeros(L+1,1); % size S
S(1) = a*(r^0); % this corresponds to S[0] in your equation
for m = 2:L+1
S(m) = S(m-1) + a*(r^m);
end
Note how the above assumes that S is a recurrence relation. We can then plot it as
plot(S,0:L)
xlabel('Value of "S"');
ylabel('Value of "L"');
title('a = 11; r = 0.9; L = 19')
Try it and see what happens!

Plus de réponses (1)

Jan
Jan le 23 Nov 2014
When you omit the clear all you can use the debugger to find out the reason of your problem.

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