RWT=cm$fit*(1-cm$fit)
Y0=log(cm$fit/(1-cm$fit))
Y=Y0+(y-cm$fit)/RWT
# The following # command should be and is a
# nearly perfect fit.
#summary(lm(Y0 ~ Ag+Ch+W,weight=RWT))
one=lm(Y ~ Ag+Ch+W,weight=RWT)