I have been searching for ways to obtain these for combinations of fixed factors and levels other than the 'baseline' group (contrasts coded all 0's) from a mixed-effects model in lme. I've modelled the continuous variable y as a function of a continuous covariate x, and fixed factors A, B, and C. The fixed factors have two levels each and I'd like to know whether the relationship between y and x varies between levels of the factors, and whether there are any interactions between these factors. I've therefore setup the model as this:
lme.fit <- lme(y ~ x*A*B*C, data=df, random=~x | subjectID)
The contrasts are default ("contr.treatment" and "contr.poly"). As usual, the summary provides the coefficients for the 'baseline' group. The rest of coefficients correspond to *differences* and their standard error with respect to this group. One can calculate the coefficients for any combination of factor levels by adding the appropriate coefficients in the results. However, I don't understand how to obtain the standard errors for these from the summary report. Can someone please let me know how to obtain these?
Cheers, Sebastian
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