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

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!

Answer 1

[the cyclist]

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

[Luca Morena]

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

[Image Analyst]

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.

Answer 2

[Image Analyst]

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')

Adapt as needed.

[Luca Morena]

This works too! thanks!