[R] date Axes and formats in lattice plots

[Deepayan Sarkar]

On Sunday 04 July 2004 21:02, Toby.Patterson at csiro.au wrote:
> All,
>
> I have some data of animal movements that I'm plotting using xyplot()
> from lattice. I want to have the date (class POSIXct object) on the
> Y-axis and the animals longitude on X-axis. Eg.
>
> xyplot(date ~ longitude, groups = animal, data = my.data)
>
> with data like:
>
>      animal   ptt year month day    lon                date
> 125 03P0014 13273 2003     7  10 150.38 2003-07-10 14:03:48
> 126 03P0192 20890 2003     7  10 151.13 2003-07-10 14:00:47
> 127 03P0197 30466 2003     7  10 150.74 2003-07-10 14:02:21
> ...etc
>
> It all works fine except for the format of the dates that gets
> displayed.
>
> I am not sure what I need to change within the lattice frame work to
> get a specific date format (eg. "%Y-%-m-%d"). Does anyone have any
> tips or, even better, some example code that they could pass on?

For R 1.9.0 and above, you should be able to do this with 

xyplot(date ~ longitude, groups = animal, data = my.data,
       scales = list(y = list(format = "%Y-%-m-%d")))

Deepayan