Subscript indices must either be real positive integers or logicals how can I fix it?

I am trying to plot this equation but I get error message.

K=9*10^9;   e= 1.6*10^-19;  p=0.33*10^-10; Alpha=1.09*10^3;
r=10^-10*linspace(33,500,10 );

V(r)=-K*(e^2./r)+ Alpha*exp(-r./p);
whos
plot(r,v);

Answer 1

[Walter Roberson]

You cannot fix it without changing what you are trying to do. You need to decide whether you are trying to define a formula for V(r), or if you are trying to assign V as an array of results. As a formula, you could have V(r) on the left hand side, but you would have had to not assign specific numeric values to r. If you are trying to assign V as an array of results, then you cannot use V(r) because you cannot index arrays at floating point numbers.

Your easiest fix would be

V=-K*(e^2./r)+ Alpha*exp(-r./p);
plot(r, V);

https://www.mathworks.com/matlabcentral/answers/305346-error-in-defining-variable-equation

Answer 2

[fs]

Thank you very much for a quick respond and clear explanation.