David,

Please read the first two paragraphs of Details from ?formula

You can try out the formulas with the notation

> expand.formula <- function(f) colnames(attr(terms(f), "factors"))
> expand.formula(~a+b)
[1] "a" "b"
> expand.formula(~a:b)
[1] "a:b"
> expand.formula(~a*b)
[1] "a"   "b"   "a:b"
> expand.formula(~a/b)
[1] "a"   "a:b"
>

See a design text for more information.

Rich


On Tue, May 10, 2011 at 4:51 PM, Rovinpiper <david.j.meehan@gmail.com>wrote:

> So what is the difference between a colon and an asterisk in this code? For
> that matter what does the slash mean?
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/ANOVA-1-too-few-degrees-of-freedom-tp3493349p3512977.html
>  Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]

