R help - Jul 2009 - How to re-order panels and y-axis values in trellis display using lattice

Hi,

I have been trying to re-order several items in a trellised barchart 
display in lattice, but can't seem to figure it out.

###sample code, Stage and Colony have 2 and 3 levels respectively.

barchart(Activity ~ Percent | Stage + Colony, data = Percent.df,
  horizontal = TRUE, layout = c(2,3),
  xlab = "Percent Time Engaged in Activity",
  ylab = "Activity")

This essentially produces the display I would like, only I would like to 
have the second column first and the first and third panels switched.  In 
addition, I would like to re-order the y-axis labels ("Activities") so
that they are in alphabetical order starting with A at the top...currently 
A is at the bottom.  I have been able to switch the actual data in the 
panels useing barchart(rev(Activity~ Percent...but cannot get the actual 
labels to switch.  Thanks in advance.

Peter

USF&WS
San Francisco Bay National Wildlife Refuge Complex
Common Murre Restoration Project
peter_kappes@fws.gov

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On Tue, Jul 7, 2009 at 3:03 PM, <Peter_Kappes at fws.gov>
wrote:
> Hi,
>
> I have been trying to re-order several items in a trellised barchart
> display in lattice, but can't seem to figure it out.
>
> ###sample code, Stage and Colony have 2 and 3 levels respectively.
>
> barchart(Activity ~ Percent | Stage + Colony, data = Percent.df,
> ?horizontal = TRUE, layout = c(2,3),
> ?xlab = "Percent Time Engaged in Activity",
> ?ylab = "Activity")
>
> This essentially produces the display I would like, only I would like to
> have the second column first and the first and third panels switched. ?In
> addition, I would like to re-order the y-axis labels
("Activities") so
> that they are in alphabetical order starting with A at the top...currently
> A is at the bottom. ?I have been able to switch the actual data in the
> panels useing barchart(rev(Activity~ Percent...but cannot get the actual
> labels to switch. ?Thanks in advance.
You need to read up on levels() of factors; in both cases, the
ordering is determined by the levels, which are by default ordered
lexically for character vectors, but can be specified manually, e.g.

factor(Activity, levels = rev(sort(unique(Activity)))

For the first question, there is a shortcut to reorder levels of
conditioning variables:

p <- barchart(Activity ~ Percent | Stage + Colony, data = Percent.df, ...)
p[, c(2, 3, 1)]

-Deepayan