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    %% Determine Observations Influential on Fitted Response Using Dffits  
% This example shows how to determine the observations that are influential
% on the fitted response values using |Dffits| values.   Load the sample
% data and define the response and independent variables. 

% Copyright 2015 The MathWorks, Inc.

load hospital
y = hospital.BloodPressure(:,1);
X = double(hospital(:,2:5)); 

%% 
% Fit a linear regression model. 
mdl = fitlm(X,y);  

%% 
% Plot the Dffits values. 
plotDiagnostics(mdl,'Dffits')    

%%
% The influential threshold limit for the absolute value of Dffits in this
% example is 2*sqrt(5/100) = 0.45. Again, there are some observations with
% Dffits values beyond the recommended limits.  

%% 
% Find the Dffits values that are large in absolute value. 
find(abs(mdl.Diagnostics.Dffits)>2*sqrt(4/100))