[R] npc to native coordinates for xyplot
deepayan.sarkar at gmail.com
Mon Sep 1 19:39:25 CEST 2008
On 9/1/08, Jason Pare <jay.pare at gmail.com> wrote:
> I am having trouble adding symbols to grid graphics. I am able to
> create a lattice scatterplot using xyplot, which has a range from
> -15:15 in both the X and Y directions. However, when I try to add
> circles and text to this graph using grid.circle() and grid.text(),
> they are offset using the default npc coordinates.
> Nothing happens when I pass the parameter default.units="native" to
> grid.circle, as suggested in this
> post:http://tolstoy.newcastle.edu.au/R/e4/help/08/03/5534.html. I also
> tried replicating the code in Paul Murrell's GridBase documentation,
> but to no avail:
> xyplot(y ~ x, groups=pt, data=dt)
> vps <- baseViewports()
> pushViewport(vps$inner, vps$figure, vps$plot)
> grid.circle(x=unit(-6,"native"), y=unit(-8,"native"), r=1)
> Is there some other parameter or command that will convert the
> grid.circle() NPC coordinates to the native coordinates within my
> xyplot graph, and not the absolute dimensions of the viewport? I am
> new to creating viewports and grid graphics in general, so any help
> would be much appreciated.
I'm not sure why you are using baseViewports(); xyplot() uses grid,
not base graphics.
lattice provides means to access (most of) the viewports it creates.
You could do:
xyplot(y ~ x, groups=pt, data=dt)
grid.circle(x=unit(-6,"native"), y=unit(-8,"native"), r=1)
There are other ways to do this too.
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