How can I save "alpha" and "beta" parameters as double using fitdist command?

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Luca Morena 2023-5-29

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https://ww2.mathworks.cn/matlabcentral/answers/1975224-how-can-i-save-alpha-and-beta-parameters-as-double-using-fitdist-command

评论： Image Analyst 2023-5-30

采纳的回答： the cyclist

Hi everyone,

I'm having problems when trying to save "alpha" and "beta" parameters when using the fitdist command.

CC is a vector of 1000 elements, I need to save a and b. I need this because I have 50 vectors for which I need to find the beta distribution that better represent my distribution of 1000 elements, and I would like to use a loop to automatically save in a .txt or .xlxs file all those a and b values. but PD is a betaDistribution object and I encounter some errors when trying to take a and b out of PD. In the Beta probability distribution object Matlab page, I can't find the command to save a and b. Of course one option would be to save them manually.

Thanks in advance,

Have a nice day!

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Answer 1

the cyclist 2023-5-29

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在 MATLAB Online 中打开

I'm not sure what part is giving you trouble. Here is how to pull the parameter values out of the distribution object. (The full double-precision value is extracted, but only significant figures after the decimal are displayed.)

The variable parameterValues can then be saved to file.

load patients

x = Weight;

pd = fitdist(x/max(x),'Beta')

pd =

BetaDistribution Beta distribution a = 3.37624 [2.35993, 4.83022] b = 0.961082 [0.905778, 1.01976]

parameterValues = pd.ParameterValues

parameterValues = 1×2

3.3762 0.9611

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Luca Morena 2023-5-30

I only needed to take a and b out of fitdist, this works! thanks!

Image Analyst 2023-5-30

You can get those directly, as I showed below. Plus you need to put them into an array because you said you have 50 files that you have to do this for. I also showed that below. I also showed how to save all 50 of them to a file with writetable.

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Answer 2

Image Analyst 2023-5-29

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https://ww2.mathworks.cn/matlabcentral/answers/1975224-how-can-i-save-alpha-and-beta-parameters-as-double-using-fitdist-command#answer_1246634

在 MATLAB Online 中打开

Try this (untested):

% Preallocate a and b column vectors.  One element for each file.
a = zeros(50, 1);
b = zeros(50, 1);
% Get distributions from 50 files.
for k = 1 : 50 % for all 50 files
    % Get distribution for this file
    pd = fitdist(x/max(x),'Beta')
    % Extract a and b values from the output and store them in column vectors.
    a(k) = pd.a
    b(k) = pd.b
end
% Create table from the two column vectors:
t = table(a, b, 'VariableNames', {'a', 'b'})
% Write table out to disk:
writetable(t, 'ab.xlsx')