PDF function does not give same result as normpdf
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George Ansari
le 21 Août 2017
Réponse apportée : Star Strider
le 21 Août 2017
Hello all, I'm using the following function to create the PD of a RV
function [ X, f ] = Normdist( mu, sigma, min_x, max_x, n )
X = zeros(n,1);
x = min_x;
dx = (max_x - min_x)/n;
for k = 1:n
X(k) = x;
f(k) = 1/sqrt(2*pi*sigma)*exp(-(x-mu)^2/(2*sigma));
x = x+dx;
end
end
I call it as follows:
[LRV, LPDF] = Normdist(0, 2.5, -10, 10, 7);
LRV = [-10; -7,142; -4,285; -1,428; 1,428; 4,285; 7,14]
but when I call:
A = normpdf(linspace(-10,10,7),0,2.5)
I get:
A = [5,353; 0,004; 0,065; 0,159; 0,065; 0,004; 5,353]
what is wrong with the function? George.
Réponse acceptée
Star Strider
le 21 Août 2017
You need to calculate ‘x’ differently (so that it creates the same interval that linspace does), and square ‘sigma’ in the denominator of the exp argument:
X = zeros(n,1);
f = zeros(n,1);
x = min_x;
dx = (max_x - min_x)/(n - 1);
for k = 1:n
X(k) = x;
f(k) = 1/(sqrt(2*pi)*sigma)*exp(-(x-mu)^2/(2*sigma^2));
x = x+dx;
end
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