R help - Jun 2005 - problem with chron scales in lattice

I can't get the scales parameter in xyplot of lattice to work as I
expected.  I'm using R-2.1.0 and lattice 0.11-8.  There should be year
labels from 1992 to 2004 for the x axis in the plot below, but instead
only a few of them appear, and in the wrong spots, as if the coordinate
system has changed after finishing with the panel function.

library(chron)
library(lattice)

# vertical grid lines at start of each year
startdate <- "1/1/1992"
enddate   <- "1/1/2005"
startdatetime <- chron(dates=startdate, times="00:00:00")
enddatetime <- chron(dates=enddate, times="00:00:00")
x.lines <- as.chron(seq.dates(startdate, enddate, by="years"))
x.limits <- c(as.chron(startdate), as.chron(enddate))

# year labels on x axis (centered between grid lines)
x.at <- as.chron(seq.dates("7/1/1992", "7/1/2004",
by="years"))
x.labels <- format(as.Date(dates(x.at)), "%Y")

# dummy data
x <- x.at[1:2]
y <- c(105, 105)
id <- c(1,2)

print(xyplot(y ~ x | id,
   panel = function(x, y, subscripts, ...) {
     panel.abline(v = x.lines, col = "lightgray", lty = 1, lwd= 1.0)
     # function to plot data would go here
   },  # end of panel
   as.table=T, layout=c(1,2), main="",
   xlim=x.limits, 
   scales = list(x = list(alternating = T, at = x.at, labels = x.labels,
tck=0)),
   strip = F
 ) # end xyplot()
) # end print()

Thanks for any help,

Scott Waichler
Pacific Northwest National Laboratory
scott.waichler at pnl.gov

> > I can't get the scales parameter in xyplot of lattice to work as I
> > expected.  I'm using R-2.1.0 and lattice 0.11-8.  There should be
year 
> > labels from 1992 to 2004 for the x axis in the plot below, but
instead 
> > only a few of them appear, and in the wrong spots, as if the 
> > coordinate system has changed after finishing with the panel
function.
> I'll try to figure out what the problem is. A temporary 
> workaround is to 
> explicitly coerce x.limits and x.at to numeric:
> 
>     ...
>     xlim = as.numeric(x.limits),
>     scales = list(x = list(alternating = T, 
>                   at = as.numeric(x.at), 
>                   labels = x.labels, tck=0)),
>     ...
Thanks, Deepayan.  I thought I had already thoroughly tried as.numeric
around the chron objects, but apparently not.  

Scott Waichler

On Wednesday 01 June 2005 12:12, Waichler, Scott R
wrote:
> I can't get the scales parameter in xyplot of lattice to work as I
> expected.  I'm using R-2.1.0 and lattice 0.11-8.  There should be year
> labels from 1992 to 2004 for the x axis in the plot below, but instead
> only a few of them appear, and in the wrong spots, as if the coordinate
> system has changed after finishing with the panel function.
This is rather odd. The coordinate system seems fine, since the following 
works as it should:


trellis.focus("panel", 1, 2)
panel.axis(side = "top", at = as.numeric(x.at), 
          outside = F, half = F, labels = x.labels, 
          rot = 0)

I'll try to figure out what the problem is. A temporary workaround is to 
explicitly coerce x.limits and x.at to numeric:

    ...
    xlim = as.numeric(x.limits),
    scales = list(x = list(alternating = T, 
                  at = as.numeric(x.at), 
                  labels = x.labels, tck=0)),
    ...

> library(chron)
> library(lattice)
>
> # vertical grid lines at start of each year
> startdate <- "1/1/1992"
> enddate   <- "1/1/2005"
> startdatetime <- chron(dates=startdate, times="00:00:00")
> enddatetime <- chron(dates=enddate, times="00:00:00")
> x.lines <- as.chron(seq.dates(startdate, enddate, by="years"))
> x.limits <- c(as.chron(startdate), as.chron(enddate))
>
> # year labels on x axis (centered between grid lines)
> x.at <- as.chron(seq.dates("7/1/1992", "7/1/2004",
by="years"))
> x.labels <- format(as.Date(dates(x.at)), "%Y")
>
> # dummy data
> x <- x.at[1:2]
> y <- c(105, 105)
> id <- c(1,2)
>
> print(xyplot(y ~ x | id,
>    panel = function(x, y, subscripts, ...) {
>      panel.abline(v = x.lines, col = "lightgray", lty = 1, lwd=
1.0)
>      # function to plot data would go here
>    },  # end of panel
>    as.table=T, layout=c(1,2), main="",
>    xlim=x.limits,
>    scales = list(x = list(alternating = T, at = x.at, labels = x.labels,
> tck=0)),
>    strip = F
>  ) # end xyplot()
> ) # end print()
>
> Thanks for any help,
>
> Scott Waichler
> Pacific Northwest National Laboratory
> scott.waichler at pnl.gov