Dear All:
I tried to replicate a case study described by Prof. Harrell in Chapter 7 of
his Regression Modeling Strategies book, but failed on using anova.Design to
reproduce his table 7.1, Following is the code:
rm(list=ls())
library(Hmisc)
library(Design)
getHdata(counties)
counties$older <- counties$age6574 + counties$age75
label(counties$older) <- '% age >= 65, 1990'
counties$pdensity <- log10(counties$pop.density+1)
label(counties$pdensity) <- 'log 10 of 1992 pop per 1990 miles^2'
dd <- datadist(counties)
options(datadist='dd')
f <- ols(democrat ~ rcs(pdensity,4) + rcs(pop.change,3) + rcs(older,3) +
crime + rcs(college,5)
+ rcs(income,4) + rcs(college,5) %ia% rcs(income,4) + rcs(farm,3) +
rcs(white,5) +
rcs(turnout,3), data=counties)
f
an <- anova(f)
and the error message reads as:
Error in solvet(cov[idx, idx], coef[idx], tol = tol) :
apparently singular matrix
Does anyone have a clue?
Thanks
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