xyplot() - can you control how the plots are ordered?

The output of the xyplot() is sorted by the alphabetical order of 
months (First Apr, then Aug so on). I need to output such that the 
order of the months is maintained, i.e. plot of Jan first, then Feb, Mar
... so on.

Hi,

I want to control the plots in the output of the xyplot(). It is
easier to explain it through an example:

#-------------------------------------------------------------
library(lattice);
# months
months <- c("Jan", "Feb", "Mar",
           "Apr", "May", "Jun",
           "Jul", "Aug", "Sep",
           "Oct", "Nov", "Dec");

n <- length(months);
m <- 10;

mdata <- data.frame(x = runif(m*n), y = runif(m*n), z = rep(months,
each = m));
h <- xyplot(y ~ x | z, data = mdata);
plot(h);
#-------------------------------------------------------------

The output of the xyplot() is sorted by the alphabetical order of
months (First Apr, then Aug so on). I need to output such that the
order of the months is maintained, i.e. plot of Jan first, then Feb,
Mar ... so on.

I tried searching on the web and I couldn't find any or probably
didn't understand. I would be much obliged if someone could help.

Thanks
Anand.

I want to control the plots in the output of the xyplot(). It is
easier to explain it through an example:

The output of the xyplot() is sorted by the alphabetical order of
months (First Apr, then Aug so on). I need to output such that the
order of the months is maintained, i.e. plot of Jan first, then Feb,
Mar ... so on.

AR<anandram <at> gmail.com> writes:

I want to control the plots in the output of thexyplot(). It is
easier to explain it through an example:

.. modified example see below

The output of thexyplot() is sorted by the alphabetical order of
months (First Apr, then Aug so on). I need to output such that the
order of the months is maintained, i.e. plot of Jan first, then Feb,
Mar ... so on.

The bad thing happens during the implicit conversion to factors
byxyplot. Create your factors explicitly, and make sure the
given order is used instead of the default
sort(unique.default(x), na.last = TRUE)
You probably also would like to add as.table = TRUE to
get Jan at the top.

Dieter

library(lattice);
# months
months <- c("Jan", "Feb", "Mar",
? ? ? ? ? ?"Apr", "May", "Jun",
? ? ? ? ? ?"Jul", "Aug", "Sep",
? ? ? ? ? ?"Oct", "Nov", "Dec")
months = factor(months,levels=months)

n <- length(months);
m <- 10;

mdata <- data.frame(x = runif(m*n), y = runif(m*n), z = rep(months,
each = m));
h <-xyplot(y ~ x | z, data = mdata,as.table=TRUE);
plot(h);