Attempted to access (5,0); index must be a positive integer or logical

Dear all, when I tried to plot the T vs. s diagram, the error "Attempted to access (5,0); index must be a positive integer or logical." shows up. When I switch T=0:1:30 to T=1:1:30, the diagram is very wrong. The good diagram only comes when I set t = 1:length(T). Could someone tells me why? Thanks a lot.

clear all;

Sigma = 5:5:30;

T = 0:1:30;

for sigma = Sigma;

    for t = T;

s(sigma,t) = (sigma-3+0.072*t*(1+0.072*t))/0.77;

    end;

end;

plot(s,T);

Answer 1

[the cyclist]

Is it better if you do this instead?

s(sigma,t+1) = (sigma-3+0.072*t*(1+0.072*t))/0.77;

Notice that I shifted your index, so that you start at 1 instead of 0.

[Michael Wolf]

Thank you, but is there anyway I could start at t = 0? Because t is temperature here, and t = 0 or negative integrals does make sense.

[the cyclist]

MATLAB has a 1-based indexing system, so you cannot write to the "zeroth element" of an array. Similarly, even if you wanted to plot at t=0.5, you could not write to the "0.5th element" of an array.

You just need to make a mapping from the values of t to the indices of your array. In this case, it is simply adding 1 to the value of t. You just need to be careful to label your resulting axes correctly

[Michael Wolf]

Thanks a lot!