how to resolve this error in for loop

T(0)=.1;I(0)=0;V(0)=.1;P=.1;Alpha=.02;beta=.3;l=2.4;K=.0027;Tmax=1500;N=10;r=3;mu=.9;eta=.99;nu=1;

T(1)=(.397953)/gamma(mu+1); I1=(.000027)/gamma(eta+1); V1=-.24/gamma(nu+1);

for k=1:10

T(k+1)=(gamma(k*mu+1)/gamma(k*mu+mu+1))*( ((r-Alpha)*T(k))-((r/Tmax)*

(symsum(T(n)T(k-n),n,[0 k])- symsum(T(n)I(k-n),n,[0 k]))-K(symsum(V(n)T(k-n),n,[0 k])));

I(k+1)= (gamma(k*eta+1)/gamma(k*eta+eta+1))*((K*(symsum(V(n)T(k-n),n,[0 k]))-beta*I(k));

V(k+1)= (gamma(k*nu+1)/gamma(k*nu+nu+1))*((N*beta*I(k))-(l*V(k)));

end

Attempted to access (0); index must be a positive integer or logical.

[Torsten]

MATLAB array indices start at 1, not at 0.

Thus T(0), I(0),V(0), symsum(T(n)T(k-n),n,[0 k]),... all throw an error.

[Jan]

I get a different message, when I run your code:

T(0)=.1;I(0)=0;V(0)=.1;P=.1;Alpha=.02;beta=.3;l=2.4;K=.0027;Tmax=1500;N=10;r=3;mu=.9;eta=.99;nu=1;
T(1)=(.397953)/gamma(mu+1); I1=(.000027)/gamma(eta+1); V1=-.24/gamma(nu+1);
for k=1:10
    T(k+1)=(gamma(k*mu+1)/gamma(k*mu+mu+1))*( ((r-Alpha)*T(k))-((r/Tmax)* ...
    (symsum(T(n)T(k-n),n,[0 k])- symsum(T(n)I(k-n),n,[0 k]))-K(symsum(V(n)T(k-n),n,[0 k])));

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

    I(k+1)= (gamma(k*eta+1)/gamma(k*eta+eta+1))*((K*(symsum(V(n)T(k-n),n,[0 k]))-beta*I(k));
    V(k+1)= (gamma(k*nu+1)/gamma(k*nu+nu+1))*((N*beta*I(k))-(l*V(k)));
end

Please post the code you really use or a minimal working example.

Torsten's suggestion is fundamental already.

By the way, in which Matlab version do you get the message "Attempted to access (0); index must be a positive integer or logical." ? And why is this clear message not an explanation already?

Answer 1

[Pooja Kumari]

Dear Neelu,

I am Pooja Kumari and it is my understanding that you are facing “index must be positive integer or logical” error in your code.

I tried to run the above code and I got the following error:

The reason for this error is incorrect delimiters and missing multiplication operator.

%above code 
T(0)=.1;I(0)=0;V(0)=.1;P=.1;Alpha=.02;beta=.3;l=2.4;K=.0027;Tmax=1500;N=10;r=3;mu=.9;eta=.99;nu=1;
T(1)=(.397953)/gamma(mu+1); I1=(.000027)/gamma(eta+1); V1=-.24/gamma(nu+1);
for k=1:10
T(k+1)=(gamma(k*mu+1)/gamma(k*mu+mu+1))*( ((r-Alpha)*T(k))-((r/Tmax)*(symsum(T(n)T(k-n),n,[0 k])- symsum(T(n)I(k-n),n,[0 k]))-K(symsum(V(n)T(k-n),n,[0 k])));
                                        1                                       2                            2                             2        
I(k+1)= (gamma(k*eta+1)/gamma(k*eta+eta+1))*((K*(symsum(V(n)T(k-n),n,[0 k]))-beta*I(k));
                                            1               2
V(k+1)= (gamma(k*nu+1)/gamma(k*nu+nu+1))*((N*beta*I(k))-(l*V(k)));
end

% I have marked 1 for incorrect delimiter
% And 2 for missing multiplication operator. 

You can use Code Analyzer to resolve this error. Refer to the link below for this purpose:

https://in.mathworks.com/help/matlab/matlab_prog/check-code-for-errors-and-warnings.html

The second error “index must be positive integer or logical “occurs because you are attempting to index variable with 0.

MATLAB supports 1-indexing.

You can understand that Array Indexing in MATLAB starts from 1 from the link provided below:

https://in.mathworks.com/help/matlab/learn_matlab/array-indexing.html

Sincerely,

Pooja Kumari