lattice: adding text between grouped panels?

How one can add a text (e.g. the labels of an axis)
in a space between grouped panels which was created
by using the argument ``between''?

Example:
	data(barley)
	dotplot(variety ~ yield | site * year, data=barley,
		between=list(x=c( 0, 0, 6 ))
How to add labels for the y axis in the space in the middle?

Formally, there's no mechanism to do that. However, most reasonable usage can 
be achieved by the panel function, e.g. (to add a y-axis tick and label at 
the mean y-value):

panel = function(x, y, ...) {
    panel.xyplot(x, y, ...)
    grid.yaxis(at = mean(y))
}

Normally, this would not work because all graphical output produced by the 
panel function is 'clipped', i.e., anything falling outside the panel is not 
drawn. This can be controlled by the setting

trellis.par.get("clip")

$panel
[1] TRUE

$strip
[1] TRUE


So you need to do something like

lset(list(clip = list(panel = FALSE)))

before calling xyplot (or whatever). Of course, turning clipping off has the 
disadvantage that unintended things can happen. Most panel functions are 
safe, but some are not (like panel.abline).


Just in case you missed it, there's a much safer way to add customized tick 
marks and labels to each panel, using the scales argument. From ?xyplot, 


  scales: list determining how the x- and y-axes (tick marks and

          [...]

          at: location of tick marks along the axis (in native
          coordinates), or a list as long as the number of panels
          describing tick locations for each panel.

          labels: Labels (strings or expressions) to go along with
          'at'. Can be a list like 'at' as well.

But this may not be what you want.

Hth,

Deepayan

--- In reply to Deepayan Sarkar: ---

Date:    20.01.04 10:40 (-0600)

Thank you again for your very helpful and inspiring answer!
Some additional questions will follow below.

On Tuesday 20 January 2004 04:14, Wolfram Fischer wrote:

How one can add a text (e.g. the labels of an axis)
in a space between grouped panels which was created
by using the argument ``between''?

Example:
	data(barley)
	dotplot(variety ~ yield | site * year, data=barley,
		between=list(x=c( 0, 0, 6 ))
How to add labels for the y axis in the space in the middle?

Formally, there's no mechanism to do that. However, most reasonable usage can 
be achieved by the panel function, e.g. (to add a y-axis tick and label at 
the mean y-value):

panel = function(x, y, ...) {
    panel.xyplot(x, y, ...)
    grid.yaxis(at = mean(y))
}

Normally, this would not work because all graphical output produced by the 
panel function is 'clipped', i.e., anything falling outside the panel is not 
drawn. This can be controlled by the setting

trellis.par.get("clip")

$panel
[1] TRUE

$strip
[1] TRUE


So you need to do something like 

lset(list(clip = list(panel = FALSE)))

before calling xyplot (or whatever). Of course, turning clipping off has the 
disadvantage that unintended things can happen. Most panel functions are 
safe, but some are not (like panel.abline).

This good idea seams to work. But:

- How can I determine in which panel I am?
  Principally I could to that by using a strip function.
  But the presence of a strip function allways (?) allocates
  space for the strip(s). How can I determine the panel
  when I don't want to display strips?

Just in case you missed it, there's a much safer way to add customized tick 
marks and labels to each panel, using the scales argument. From ?xyplot, 


  scales: list determining how the x- and y-axes (tick marks and

          [...]

          at: location of tick marks along the axis (in native
          coordinates), or a list as long as the number of panels
          describing tick locations for each panel.

          labels: Labels (strings or expressions) to go along with
          'at'. Can be a list like 'at' as well.

But this may not be what you want.

Thanks for this hint!

When I wanted add labels to each panel group of:

	my.barley <- subset( barley, ! ( site == "Grand Rapids" & year == "1932" ) )

	with( my.barley, dotplot(variety ~ yield | year * site, layout=c(6,2)
		, between=list(x=c(0,6))))


I tried:
	with( my.barley, dotplot(variety ~ yield | year * site, layout=c(6,2)
		, scales=list( rot=0, y=list( relation='sliced'
		, at = rep( list( 1: nlevels( variety ), NULL ), 6 )))))

I used:
- ``sliced'' because there was an error when I did not use it:
	"the at and labels components of scales may not be
	lists when relation = same".
- the at-option to eliminate the yaxis-labels within the panel groups.

I received:
- Several warning messages.
- No axis labels for panel groups with an empty first panel.
- Gigant scales in the second panels of each panel group.

What can I do to:
- Have normal scales in the second panels of each panel group?
- Eliminate the space between the first and the second panel
  in each group.

Hth,

Deepayan

Thanks! Wolfram