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
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