I'd like to make a less than full rank design using dummy variables
for factors. Here is some example data:
when <- data.frame(time = c("afternoon", "night", "afternoon",
"morning", "morning", "morning",
"morning", "afternoon", "afternoon"),
day = c("Monday", "Monday", "Monday",
"Wednesday", "Wednesday", "Friday",
"Saturday", "Saturday", "Friday"))
For a single factor, I can do this this using
> head(model.matrix(~time -1, data = when))
timeafternoon timemorning timenight
1 1 0 0
2 0 0 1
3 1 0 0
4 0 1 0
5 0 1 0
6 0 1 0
but this breakdown muti-variable formulas such as "time + day" or
"time + dat + time:day".
I've looked for alternate contrast functions to do this and I haven't
figured out a way to coerce existing functions to get the desired
output. Hopefully I haven't missed anything obvious.
Thanks,
Max
> sessionInfo()
R version 2.11.1 Patched (2010-09-11 r52910)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
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