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. Also, can any of these functions be applied to glmmPQL mixed models? Thanks very much Jo Halliday
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 > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html >-- Frank E Harrell Jr Professor and Chair School of Medicine Department of Biostatistics Vanderbilt University