[R] Using "|"

[Sundar Dorai-Raj]

Jim Milks wrote on 5/3/2005 8:34 AM:
> Dear all,
> 
> I have a rodent dataset that I am reanalyzing.  The set consists of 
> several variables (#Microtus captured, Grass stems/m^2, etc), among 
> which is a Grid factor variable c(North,South).  I have evidence that 
> there are significant differences in vegetation and rodent populations 
> between the two locations (from chi-square tests) and would like to run 
> separate analyses along North/South lines on the rest of my data.  For 
> example, I type:
> 
>  > plot(Microtus.T~Grass | Grid)
> 
> However, I get the following:
> 
> Error in plot.window(xlim, ylim, log, asp, ...) :
>     need finite xlim values
> In addition: Warning messages:
> 1: "|" not meaningful for factors in: Ops.factor(Grass, Grid)
> 2: no finite arguments to min; returning Inf
> 3: no finite arguments to max; returning -Inf
> 
> Other than adding xlim arguments, what else can I do, especially in 
> light of warning message 1?
> 
> Thank you in advance.
> 
> Sincerely,
> Jim Milks


Are you confusing "plot.formula" with "lattice:xyplot"? Your example 
should work if you use:

library(lattice)
xyplot(Microtus.T ~ Grass | Grid)

HTH,

--sundar