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

Question

Santtu Söderholm 2016-9-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/304344-error-subscript-indices-must-either-be-real-positive-integers-or-logicals

关闭： MATLAB Answer Bot 2021-8-20

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?

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Answer 1

Walter Roberson 2016-9-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/304344-error-subscript-indices-must-either-be-real-positive-integers-or-logicals#answer_235955

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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.