Error: Subscript indices must either be real positive integers or logicals

The following code produces the error in the title:

 syms x;
 % Alkuarvoja
 n = 100;
 P = 0.02;
 lambda = n*P; % Poissonin parametri

 % Tiheysfunktiot

 b(x) = nchoosek(n,x) * P^x * (1-P)^(n-x); % Binomi

 p(x) = (lambda^(x))/(exp(-lambda) * factorial(x)); % Poisson

 % Todennäköisyydet

 Pb = 0; % Binomi

 Pp = 0; % Poisson

 % Binomilaskenta

 for i = 0:1:2

    Pb = Pb + b(i);

 end

 % Poissonin approksimaatio
 for i = 0:1:2
    Pp = Pp + P(i);
 end

 Pp = 1 - Pp;

 Pb = vpa(Pb);
 Pp = vpa(Pp);

 disp(Pb)

 disp(Pp)

Any idea what might be causing it?

Answer 1

[Walter Roberson]

You have

 for i = 0:1:2
    Pp = Pp + P(i);
 end

MATLAB is case sensitive, so the P there refers to

P = 0.02;

not to

   p(x) = (lambda^(x))/(exp(-lambda) * factorial(x)); % Poisson

We recommend avoiding using different variables that differ only in uppercase / lowercase: you can certainly do that and sometimes there are good reasons to do it, but unless there are good reasons the practice is more likely to lead to exactly this kind of confusion.