[R] problem in plotting numeric x by POSIXt class with lattice

[David Winsemius]

On Feb 19, 2011, at 11:44 AM, Aviad Klein wrote:

> # hi all,
>
> # I'm trying to plot temperatures by date in a trellis plot by their
> stations
>
> # I'm plotting the following data.frame
>
> library(lattice)
>
> h <- structure(list(station_name = structure(c(3L, 4L, 2L, 10L, 11L,
> 12L, 6L, 7L, 5L, 8L, 9L, 3L, 4L, 2L, 10L, 11L, 12L, 6L, 7L, 5L,
> 8L, 9L, 3L, 4L, 2L, 10L, 11L, 12L, 6L, 7L), .Label = c("Ashqelon",
> "Beer Sheva", "Beit Dagan", "Eden", "Ein Carmel", "Jerusalem",
> "Negba", "Nir HaEmek", "Ramat HaNegev", "Ramon", "Tel Mond",
> "Zemah"), class = "factor"), max_dry = c(23.4, 24.3, 25.5, 21.8,
> 23.1, 22, 23, 24, 22.7, 24.9, 23.3, 20.2, 20.8, 22.5, 20, 20.6,
> 20.5, 20.9, 21, 19.2, 21.8, 20.7, 21, 21.8, 20.2, 18.4, 20.5,
> 20.3, 17.1, 21.4), measure_date = structure(list(sec = c(0, 0,
> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 0, 0), min = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L), hour = c(0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L), mday = c(1L, 1L, 1L, 1L, 1L, 1L,
> 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,
> 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), mon = c(0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L), year = c(100, 100, 100,
> 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
> 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
> 100), wday = c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L,
> 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L,
> 5L, 5L), yday = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L,
> 2L, 2L, 2L), isdst = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L,
> 0L, 0L, 0L, 0L)), .Names = c("sec", "min", "hour", "mday", "mon",
> "year", "wday", "yday", "isdst"), class = c("POSIXlt", "POSIXt"
> ))), .Names = c("station_name", "max_dry", "measure_date"),  
> row.names =
> c(NA,
> 30L), class = "data.frame")
>
> # using the following :
>
> xyplot(max_dry~measure_date|station_name,data=h)
>
> # I receive the following error
> # Error in structure(xx, class = c("POSIXct", "POSIXt"), tzone = tz) :
> invalid 'x' argument
>
> # does anyone know why?

POSIXlt dates are not always handled well by plotting routines. Try:

 > h$measure_date <- as.POSIXct(h$measure_date)
 > xyplot(max_dry ~ measure_date | station_name, data=h)

-- 
David Winsemius, MD
West Hartford, CT