Dear experts,
I have a few quick questions related to GLMs:
1) Suppose my response is of the type Yes/No, How can I control which
response I'm modelling?
2) How can I perform Type III tests? Is it with -> drop1(mymodel,
test="Chisq") ?
3) I have a numerical variable which I converted to an ordered factor as
shown below, but in the summary results of the logistic regression I get
labels for this variable which are not the ones I specified (I get labels I
even don't know where they are coming from)?
set.seed(12345)
dv <- gl(n=2, k=1, length=20, label=c("Yes", "No"))
x1 <- rnorm(n=20, mean=100, sd=10)
x2 <- gl(n=3, k=1, length=20, label=c("x2_1", "x2_2", "x2_3"))
mydata <- data.frame(dv,x1,x2)
mydata$f.x1 <- cut(x1, breaks=c(80,90,100,120))
mydata$f.x1 <- ordered(mydata$f.x1, labels=c("L1", "L2", "L3") ,
levels(mydata$f.x1)) #Specify desired labels
mydata$f.x1
attach(mydata)
mymodel <- glm(dv ~ f.x1 + x2, family=binomial)
summary(mymodel)
drop1(mymodel, test="Chisq") #Type 3 test?
lastly,
4) how can I test statistical significance between levels of a factor?
Thanks a lot for your help!
Lars.
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