R help - Jun 2006 - lattice xyplot - aligning date labels so that they align with the grid lines in panel.grid

Hi,

I have a basic question about aligning date labels for the x-axis
in an xyplot so that they align with the grid lines
from the panel.grid argument.

For example, with

x <- data.frame(
  date = seq(as.Date("2005/01/01"), as.Date("2006/06/01"), 
  length.out = 20), value = runif(20))
xyplot(value ~ date, data = x,
  panel = function(x, y, subscripts, ...)
  { panel.grid(h = -1, v = -1, col = "grey", lwd = 1, lty = 1)
    panel.xyplot(x, y, ...)
  }) 

How can I get the labels on the x-axis to align 
with the vertical grid lines?
i.e. I have 6 vertical grid lines by default (v = -1)
in this example so I would like 6 labels along the x-axis
at the same points, whereas I see only 2 (2005 and 2006).

As an alternative I would be happy to just specify the number of labels
as long as panel.grid's vertical lines aligned with the labels.
> R.version.string
[1] "Version 2.3.1 (2006-06-01)"

on Windows NT4.

Regards,

John.

John Gavin <john.gavin at ubs.com>,
Commodities, FIRC,
UBS Investment Bank, 2nd floor, 
100 Liverpool St., London EC2M 2RH, UK.
Phone +44 (0) 207 567 4289
This communication is issued by UBS AG or an affiliate ("UBS...{{dropped}}

On 6/19/06, john.gavin at ubs.com <john.gavin at ubs.com>
wrote:
> Hi,
>
> I have a basic question about aligning date labels for the x-axis
> in an xyplot so that they align with the grid lines
> from the panel.grid argument.
>
> For example, with
>
> x <- data.frame(
>   date = seq(as.Date("2005/01/01"),
as.Date("2006/06/01"),
>   length.out = 20), value = runif(20))
> xyplot(value ~ date, data = x,
>   panel = function(x, y, subscripts, ...)
>   { panel.grid(h = -1, v = -1, col = "grey", lwd = 1, lty = 1)
>     panel.xyplot(x, y, ...)
>   })
>
> How can I get the labels on the x-axis to align
> with the vertical grid lines?
> i.e. I have 6 vertical grid lines by default (v = -1)
> in this example so I would like 6 labels along the x-axis
> at the same points, whereas I see only 2 (2005 and 2006).
You will need to do it manually, e.g.:

xyplot(value ~ date, data = x,
       panel = function(x, y, subscripts, ...) {
           panel.grid(h = -1, v = 0, col = "grey", lwd = 1, lty = 1)
           panel.abline(v = as.Date(c("2005/01/01",
"2006/01/01")),
                        col = "grey", lwd = 1, lty = 1)
           panel.xyplot(x, y, ...)
       })

For more, you can put in more locations in panel.abline, and the same
locations as tick mark positions in scales$y$at.
> As an alternative I would be happy to just specify the number of labels
> as long as panel.grid's vertical lines aligned with the labels.
Not possible currently, unlikely to be possible ever.
> > R.version.string
> [1] "Version 2.3.1 (2006-06-01)"
>
> on Windows NT4.
>
> Regards,
>
> John.
>
> John Gavin <john.gavin at ubs.com>,
> Commodities, FIRC,
> UBS Investment Bank, 2nd floor,
> 100 Liverpool St., London EC2M 2RH, UK.
> Phone +44 (0) 207 567 4289
> This communication is issued by UBS AG or an affiliate
("UBS...{{dropped}}
>
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