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How do i fit the weibull histogram?

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studentmatlaber
studentmatlaber on 29 Jun 2021
Commented: studentmatlaber on 29 Jun 2021
Hello to everyone. I'm plotting a histogram of a data I have. This distribution is most similar to the "weibull distribution". When I fit the graph with the histfit command, it does not match the graph. I found the scale and shape values of the weibull distribution with the fitdist command. I tried plotting a manual weibull distribution to fit the histogram, but it still doesn't match the histogram. I will share all the outputs with you. This is the code I wrote to draw it manually. I would be very grateful if you could tell me how to properly fit the histogram.
histfit(signalhist_poz,1000,'weibull');
histogram(signalhist_poz)
fitdist
Weibull distribution
A = 0.141626 [0.140708, 0.14255]
B = 0.652068 [0.649942, 0.654202]
PD=makedist('Weibull','a',0.141626,'b',0.652068)
X = 0:.01:1.2;
pdf_weibull = pdf(PD,X);
histogram(signalhist_poz);
hold on
plot(X,pdf_weibull,'LineWidth',2)

Accepted Answer

TADA
TADA on 29 Jun 2021
The PDF you calculated should be normalized to the area of the histogram first.
Here's how histfit does it more or less:
pd=makedist('Weibull','a',0.141626,'b',0.652068) ;
n = 1000;
signalhist_poz = PD.random(n, 1);
X = 0:.01:1.2;
pdf_weibull = pdf(PD,X);
nbins = 100;
figure(1);
clf();
h = histogram(signalhist_poz, nbins);
binedges = h.BinEdges;
hold on
plot(X,pdf_weibull,'LineWidth',2);
% Normalize the density to match the total area of the histogram
binwidth = abs(binedges(2)-binedges(1)); % Finds the width of each bin
% this is where the magic happens
area = n * binwidth;
y = area * pdf_weibull;
figure(2);
clf();
histogram(signalhist_poz, 100);
hold on;
plot(X,y,'LineWidth',2)
  4 Comments
studentmatlaber
studentmatlaber on 29 Jun 2021
Thank you very much for your help.

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