[Rd] print.trellis(..., draw.in=...)

[Deepayan Sarkar]

On 5/21/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> A year ago I had posted this code
>
> https://stat.ethz.ch/pipermail/r-devel/2005-June/033508.html
>
> and the associated discussion was that there would be a print.trellis
> argument that could be used to eliminate the need for with.vpPath
> or with.viewport there.  I assume that that is what draw.in= in
> print.trellis is for.  When I try it I get an error.  I did notice that
> ?print.trellis says draw.in= has not been well tested yet.  Is
> this a bug?

No, but perhaps a lack of clarity in the documentation. ?print.trellis says:

 draw.in: An optional (grid) viewport (used as the 'name' argument in
          'downViewport') in which the plot is to be drawn.  ...

and ?downViewport says

    name: A character value to identify a viewport in the tree.

Your code supplies viewports, not character names (in the older
working example, you did this conversion inside with.vpPath).

-Deepayan

> After running the the code at the end I get this error
> message:
>
>  Error in downViewport.vpPath(vpPathDirect(name), strict, recording =
> recording) :
>         Viewport 'viewport[GRID.VP.1]' was not found
>
> The only difference between the code below and the code in the
> link above (which works) is that in the for loop at the end the
> 'with' in the code in the link has been removed and draw.in=
> used in the print call in its place.
>
> I am using Windows XP and get similar messages in 2.2.1 and
> 2.3.0 patched.
>
>
> library(grid)
> library(lattice)
>
> pushLayout <- function(nr, nc, name="layout") {
>   pushViewport(viewport(layout=grid.layout(nr, nc), name=name))
>   for (i in 1:nr) {
>     for (j in 1:nc) {
>       pushViewport(viewport(layout.pos.row=i, layout.pos.col=j))
>       upViewport()
>     }
>   }
>   upViewport()
> }
>
> names.vpPath <- names.viewport <- function(x) x$name
>
> with.vpPath <- with.viewport <- function(data, expr, ...) {
>       # if data is a vpPath it cannot be ROOT since
>       # NULL will never dispatch here
>       depth <- if (data$name == "ROOT") 0 else downViewport(names(data))
>       result <- eval.parent(substitute(expr))
>       upViewport(depth)
>       invisible(result)
> }
>
> getChildren.viewport <- function(x) x$children
>
> grid.newpage()
>
> # specify number of cells to fill and number of rows
> n <- 5; nr <- 3
>
> nc <- ceiling(n/nr)
> downViewport(pushLayout(nr, nc))
>
> vpt <- current.vpTree(all = FALSE)
> for(k in 1:n)
>       print( xyplot(v ~ v, list(v = 1:k)), newpage = FALSE,
>                 draw.in = getChildren.viewport(vpt)[[k]] )