Re: [Rd] Re: [R] Problem going back to a viewport with gridBase

From: Paul Murrell <p.murrell_at_auckland.ac.nz>
Date: Wed 08 Jun 2005 - 03:12:29 GMT

Hi

Gabor Grothendieck wrote:
> Here is the code once again. This time I have supplied two
> names methods and a getChildren.viewport function to
> encapsulate the corresponding grid internals. It would
> be easiest if grid provided these itself but in the absence
> of that this does encapsulate dependencies on grid
> internals to a well defined set of functions. Note that
> names is only used in 'with' and 'with' will be eliminated
> once Deepayan adds the use.viewport= (or whatever
> its called) to print. I am not sure from your response
> whether or not you intend to add these items to the grid
> API but in any case this provides an intermediate
> level of safety.

Yep, I've made a note to look at adding these to the grid API. Thanks.

Paul

> 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) with(getChildren.viewport(vpt)[[k]],
> print( xyplot(v ~ v, list(v = 1:k)), newpage = FALSE )
> )

-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul@stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/

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Received on Wed Jun 08 13:23:51 2005

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