R help - Jun 2012 - exact relative positioning of lattice plots

Hello,

I have two lattice plots for which panel.height is fixed.  I am trying to
position them in a column so that there is exactly half an inch of vertical
space between them.  This would be a simple task if I were not fixing
panel.height.  But given that I am, I can't find a way to put exactly half
an inch of space between the plots.  Is there a way?

I've checked the Sarkar and Murrell books, and I've searched the
archives of this list, but I haven't found a solution.

My first approach was to set the "split", "par.settings",
and "lattice.options" arguments when creating my plots.  But I
couldn't get that approach to work.

My second approach was to use grid.layout to specify a three-row layout, with
the middle row being exactly .5" high. This lets me print one plot to the
top row and the other to the bottom row.  The problem is that I can't
vertically justify the placement of the plots within their viewports.  As a
result, I get more or less than .5" between the plots, depending on the
size of the page.  Here is a small demonstration:

# Load packages
library(grid)
library(lattice)

# Create layout and viewport
masterLayout <- grid.layout(
  nrow    = 3,
  ncol    = 1,
  heights = unit(c(1, .5, 1), c("null", "inches",
"null")),
  respect = matrix(c(0, 1, 0)))
vp1 <- viewport(layout.pos.row = 1, name = "vp1", just =
c("center", "bottom"))
vp2 <- viewport(layout.pos.row = 2, name = "spacer")    
vp3 <- viewport(layout.pos.row = 3, name = "vp3", just =
c("center", "top"))

# Create plots
theme.padding <- list(
  layout.heights = list(
    top.padding       = 0,
    main.key.padding  = 0,
    key.axis.padding  = 0,
    axis.xlab.padding = 0,
    key.sub.padding   = 0,
    bottom.padding    = 0))
myPlot <- xyplot(
  1 ~ 1,
  panel        = function () grid.rect(gp = gpar(fill="blue")),
  scales       = list(axs = 'i', draw = FALSE),
  xlab         = NULL,
  ylab         = NULL,
  par.settings = theme.padding)

# Push viewports and print plots
grid.newpage()
pushViewport(
  vpTree(
    viewport(layout = masterLayout, name="master"),
    vpList(vp1, vp2, vp3)))
seekViewport("master")
print(myPlot, draw.in = "vp1", panel.height = list(x=2,
units="in"))
print(myPlot, draw.in = "vp3", panel.height = list(x=3,
units="in"))
seekViewport("spacer")
grid.rect() 
==
Thank you for any help that you can offer.

John Bullock

On Wed, Jun 20, 2012 at 9:26 AM, John G. Bullock <john.bullock at
yale.edu> wrote:
>
> Hello,
>
> I have two lattice plots for which panel.height is fixed. ?I am trying to
position them
> in a column so that there is exactly half an inch of vertical space between
them.
> This would be a simple task if I were not fixing panel.height. ?But given
that I am,
> I can't find a way to put exactly half an inch of space between the
plots. ?Is there a way?
In your actual use case, are there any annotations outside the panel
(tick marks, labels, etc.)? Things would be much simpler if not (as in
your example). In that case, just call the suitable panel function
after setting up the proper axis limits (after doing pushViewport or
seekViewport or whatever).

If you do have extra annotation, you need to decide how much space
they should have.

-Deepayan

> In your actual use case, are there any annotations outside the panel
> (tick marks, labels, etc.)? Things would be much simpler if not (as in
> your example). In that case, just call the suitable panel function
> after setting up the proper axis limits (after doing pushViewport or
> seekViewport or whatever).
>
> If you do have extra annotation, you need to decide how much space
> they should have.
Thank you.  Yes, my actual use case does have annotations outside the panel. 
Even so, this is helpful.

John