Dear R Users,
Am using lm() with contrasts as below. If I skip the contrasts()
statement, I get the coefficient names to be
> names(results$coef)
[1] "(Intercept)" "VarAcat" "VarArat" "VarB"
which are much more meaningful than ones based on integers.
Can anyone tell me how to get R to keep the coefficient names based on the
factor levels whilst using contrasts rather than labelling them with
integers?
Many thanks in advance,
Pete
Cardiff, UK
> dt=read.table("testreg.txt",sep=",",header=T)
> dt
ID VarA VarB VarC
1 1 cat 2 23
2 2 dog 3 56
3 3 rat 5 35
4 4 cat 2 43
5 5 cat 7 51
6 6 dog 3 31
7 7 dog 4 65
8 8 rat 1 18
9 9 rat 6 49
10 10 dog 3 28
> dt$VarA=relevel(dt$VarA,ref="dog")
> treat3=matrix(-1/3,ncol=2,nrow=3); for (i in 1:2) {treat3[i+1,i]=2/3}
> contrasts(dt$VarA)=treat3
> levels(dt$VarA)
[1] "dog" "cat" "rat"
> results=lm(formula=VarC~VarA+VarB, data=dt)
> names(results$coef)
[1] "(Intercept)" "VarA1" "VarA2" "VarB"
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