Data come from the 1991 Arizona cardiovascular patient files. A subset of the fields was selected to model the differential length of stay for patients entering the hospital to receive one of two standard cardiovascular procedures: CABG and PTCA. CABG is the standard acronym for Coronary Artery Bypass Graft, where the flow of blood in a diseased or blocked coronary artery or vein has been grafted to bypass the diseased sections. PTCA, or Percutaneous Transluminal Coronary Angioplasty, is a method of placing a balloon in a blocked coronary artery to open it to blood flow. It is a much less severe method of treatment for those having coronary blockage, with a corresponding reduction in risk.
A data frame with 3589 observations on the following 6 variables.
length of hospital stay
1=Urgent/Emerg; 0=elective (type of admission)
1= Age>75; 0=Age<=75
encrypted facility code (string)
azprocedure is saved as a data frame. Count models use los as response variable. 0 counts are structurally excluded
1991 Arizona Medpar data, cardiovascular patient files, National Health Economics & Research Co.
Hilbe, Joseph M (2014), Modeling Count Data, Cambridge University Press Hilbe, Joseph M (2007, 2011), Negative Binomial Regression, Cambridge University Press Hilbe, Joseph M (2009), Logistic Regression Models, Chapman & Hall/CRC
library(MASS) library(msme) data(azprocedure) glmazp <- glm(los ~ procedure + sex + admit, family=poisson, data=azprocedure) summary(glmazp) exp(coef(glmazp)) nb2 <- nbinomial(los ~ procedure + sex + admit, data=azprocedure) summary(nb2) exp(coef(nb2)) glmaznb <- glm.nb(los ~ procedure + sex + admit, data=azprocedure) summary(glmaznb) exp(coef(glmaznb))