index must be a positive integer or logical

for i=1:1:7

    P(1)=1000;
    P(7)=500;

    f(i)=P(i-1)^2-P(i-1)*P(i)-P(i)^2+P(i)*P(i+1);

    disp f(i)
end

All my declared variables here are integers. How do I resolve this error?

Answer 1

[Azzi Abdelmalek]

when you write p(i), make sure that i is a positive integer, not equal to 0. in your case, you have p(i-1), if i is equal to 1, then i-1 will be 0, which is not allowed by Matlab as an index

[Amey]

Yes that worked! thank you.