[R] lattice shingle with time and date format

[Deepayan Sarkar]

On Tue, Feb 10, 2009 at 6:29 AM, Jon Loehrke <jloehrke at umassd.edu> wrote:
> Hi R-Users,
>
> I have a time series of bivariate observations (x,y,t).  I've
> developed a few panel routines to explore certain aspects of the data,
> and now would like to break the time series up into smaller chunks to
> explore the temporal trends.  I would like to know if anyone has any
> experience breaking up time series with lattice.
>
> Base graphics offers coplot, utilizing the co.intervals routine to
> break up the series into equal chunks.  Lattice has equal.count as a
> wrapper for co.intervals.  As you can see in the example below, I can
> recreate a 'coplot' with lattice but am having difficulty getting the
> x-axis of the shingle plot and the strip labeling on the xyplot to be
> in time or date format.  My question really consists of two parts,
> with the second part being less important for my data visualization
> purposes:
>
> 1) How might I be able to convert the x-axis of the shingle plot from
> numeric to date format?

Perhaps something like

plot(breaks, xlim = as.Date(extendrange(breaks), origin = structure(0,
class = "Date")))

or the simpler

plot(breaks, xlim = extendrange(times))

(the warning seems harmless).

> 2) How might I be able to customize the strip labels on the xyplot to
> show a range, like min(month, year)-max(month, year) for each panel?

br.levels <- sapply(levels(breaks),
                    function(x) {
                        paste(as.character(structure(x, class = "Date")),
                              collapse = ", "))

xyplot(y~x|breaks, data=df,
       strip = strip.custom(factor.levels = br.levels,
                            strip.levels = TRUE,
                            strip.names = FALSE))

You probably want a suitable 'format' in the as.character() call.

-Deepayan