R help - Nov 2010 - Aligning Grid Lines with Date Ticks in Trellis Plot

I know this issue has been discussed before, but I hoped the advent of
pretty.Date would resolve it. In the following code, the first plot produces
misaligned vertical grid lines, while in the second plot they are properly
aligned. Is there any way to get something along the lines of the first call to
produce properly aligned grid lines?

X <- data.frame(date=seq(as.Date("1990/01/01"),
as.Date("2010/11/24"), by=1))
X$value <- rnorm(length(X$date))

## This produces grid lines not aligned with the date ticks

xyplot(value ~ date, data=X,
       panel = function(...) {
         panel.grid(v=-1,h=-1,col="black")
         panel.xyplot(...)
       })

## This produces grid lines aligned with the date ticks

xyplot(value ~ date, data=X,
       panel = function(...) {
         panel.abline(v=pretty(X$date, 5))
         panel.grid(v=0,h=-1,col="black")
         panel.xyplot(...)
       })                                        

Thanks.

- Elliot

On 2010-11-24 06:59, Elliot Joel Bernstein wrote:
> I know this issue has been discussed before, but I hoped the advent of
pretty.Date would resolve it. In the following code, the first plot produces
misaligned vertical grid lines, while in the second plot they are properly
aligned. Is there any way to get something along the lines of the first call to
produce properly aligned grid lines?
>
> X<- data.frame(date=seq(as.Date("1990/01/01"),
as.Date("2010/11/24"), by=1))
> X$value<- rnorm(length(X$date))
>
> ## This produces grid lines not aligned with the date ticks
>
> xyplot(value ~ date, data=X,
>         panel = function(...) {
>           panel.grid(v=-1,h=-1,col="black")
>           panel.xyplot(...)
>         })
>
> ## This produces grid lines aligned with the date ticks
>
> xyplot(value ~ date, data=X,
>         panel = function(...) {
>           panel.abline(v=pretty(X$date, 5))
>           panel.grid(v=0,h=-1,col="black")
>           panel.xyplot(...)
>         })
>
Here are a couple of ways:

  xyplot(value ~ date, data=X, grid=TRUE)  ## or use type="g"

or

  xyplot(value ~ date, data=X,
         panel = function(x,y,...) {
           panel.grid(v=-1, h=-1, col=3, x=x, y=y,...)
           panel.xyplot(x,y,...)
         })

or, putting the grid call inside the panel.xyplot:

  xyplot(value ~ date, data=X,
         panel=function(x,y,...) {
           panel.xyplot(x, y,
                        grid=list(v=-1, h=-1,
                                 col=3, x=x, y=y), ...))
         })

Peter Ehlers
> Thanks.
>
> - Elliot