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    %% Quantile-Quantile Plot for Weibull Distribution

%%
% Use a quantile-quantile plot to determine whether sample data comes from
% a Weibull distribution.
%%
% Load the sample data.
load(fullfile(matlabroot,'examples','stats','lightbulb.mat'))

%%
% The first column of the data has the lifetime (in hours) of two types of
% lightbulbs. The second column has information about the type of light
% bulb. 1 indicates fluorescent bulbs whereas 0 indicates the incandescent
% bult. The third column has censoring information. 1 indicates censored
% data, and 0 indicates the exact failure time. This is simulated data.

%%
% Remove the censored data.
lightbulb = [lightbulb(lightbulb(:,3)==0,1),...
    lightbulb(lightbulb(:,3)==0,2)];

%%
% Create a variable for each light bulb type. Include only uncensored data.
fluo = [lightbulb(lightbulb(:,2)==0,1)];
insc = [lightbulb(lightbulb(:,2)==1,1)];

%%
% Create a Weibull probability distribution object using the default
% parameters of |A = 1| and |B = 1|.
pd = makedist('Weibull');

%%
% Create a q-q plot to determine whether the lifetime of fluorescent bulbs
% has a Weibull distribution.
figure
qqplot(fluo,pd)

%%
% The plot is not a straight line, suggesting that the lifetime
% data for fluorescent bulbs does not follow a Weibull distribution.