[R] delta-beta's

[Frank E Harrell Jr]

JEB Halliday wrote:
> Hi there
> 
> I have created a multivariate logistic regression model looking at the
> presence/absence of disease on farms.  I would like to plot the diagnostic
> plots recommended by Hosmer & Lemeshow to look particularly for any points of
> high influence.  In order to do this I need to extract values for delta-beta.
> The function dfbeta gives a value for change in each coefficient but I am
> looking for a composite value that gives an overall measure of change to the
> coefficients.  It may be that dffits is this function but I cannot gather what
> this is or what it is calculated from?
> 
> If anyone has any advice re plotting H&L logistic regression diagnostics in R
> that would be greatly appreciated.

In the Design package do ?residuals.lrm

What to do about overly influential observations is a big question 
though.  You can bias the model by removing them.

Frank

> Also, can any of these functions be applied to glmmPQL mixed models?
> 
> Thanks very much
> Jo Halliday
> 
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-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University