So is this factor ordered or not. Is it just in your model to create
unordered strata? What does the Time variable look like now?
summary(Time)
Depending on how Time and Treatment are associated with the subjects
you may choose different options. And are they sitting in a dataframe?
--
David.
On Oct 28, 2009, at 1:12 PM, Mark Kimpel wrote:
I am analyzing an experiment in which time is a factor, represented by
numbers indicating time since last treatment, but in this particular
case
there is no reason to think that time has a numeric meaning in the
sense
that 24 would be greater than 6. We have no idea which genes will be
increasing or decreasing at different times.
So I have the following model (to be applied over many genes):
mod <- lm(gene.expression ~ Treatment + Time)
If I wanted to just hack my way around this I could just paste a
character
to all of the times, but I'm curious as to the right way to do this.
What would be the correct syntax or transformation? Would Time <-
factor(as.character(Time)) do it? I want to make sure that it does
not get
coerced back to numeric.
Thanks,
Mark
Mark W. Kimpel MD ** Neuroinformatics ** Dept. of Psychiatry
Indiana University School of Medicine
15032 Hunter Court, Westfield, IN 46074
(317) 490-5129 Work, & Mobile & VoiceMail
(317) 399-1219 Skype No Voicemail please
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