Trellis graphics and clipping

Sun, Jul 29, 2001 9:34 AM

The problem lies (if I get you correctly) in the fact
that Lattice graphics devices need to be initialized
differently from usual R graphics devices. This has to
do with special requirements of the underlying grid
package, and also some standard parameter settings
associated with each device.

Upshot: you need to use

trellis.device(postscript, file = "filename.ps")

instead of 

postscript("filename.ps")

What this does (with regard to clipping) is that it
calls a grid function grid.start(). You can get almost

the same effect if you do

postscript(filename)
grid.start()

but trellis.device is the preferred way. The same goes
for the x11() device.

I would encourage you to read the ?Lattice help page
to familiarise yourself with this sort of
peculiarities.

Note: Currently, usual R graphics and lattice/grid
graphics don't mix, that is, you have to enclose any
calls to grid graphics functions (which includes all
lattice graphics functions) within calls to
grid.start() and grid.stop(). Hopefully, this will
change somewhat in the next release of lattice.

--- Ted.Harding at nessie.mcc.ac.uk wrote:

Hi again folks,

I seem to have got the trellis (lattice + grid)
business
working basically OK, in that I can get my 5x5 array
of
histograms laid out as they should be.

However, there is a behaviour I can't see my way
round.

Even when displayed in the R Graphics Window, there
is
some clipping (the extreme top, bottom, left and
right
edges are not there, so that labels, and parts of
numerical
scale markers all round, have been clipped off).

When I switch to the "postscript" device, with the
comamnd
'postscript(filename,...)', the result is even more
clipped,
in that parts of the histogram plots themselves get
cut off,
including their titles as seen in the X11 display.
On the
other hand (using gv's "position meter"), it seems
that the
internal %%BoundingBox matches the dimensions and
coordinates
of what SHOULD get displayed/printed, allowing
plenty of
"white space" round the bit of the graphic that
_does_ get
displayed, so that the whole thing could have been
fitted in
anyway.

And if I go at it crudely, simply using
'dev.print()' to
bang out a har-copy, it is even more clipped again
...

I've tried playing with all the obvious (to me)
parameters
which I can find, but it has not effect on this.

I've checked the PostScript file itself, and the
parts that
are missing are not mentioned therein, so it's not a
PostScript
"clippath" phenomenon: it's definitely R which is
deciding not
to output them.

What's needed is some way of coordinating the
dimensions of
the various levels of this process, so that the
output to X11
is scaled so that the whole graphic can fit in, and
the output
to postscript is also scaled so that it fits into
whatever
size of graphic is nominated (not that this should
be an
issue for EPS output anyway -- it would be quite
sufficient
to output everything and then put a BoundingBox
round the
lot, and never mind things like papersize and so
forth).

So I'm bewildered. And, if anyone knows a way round
it,
I'd be most obliged to hear!

With thanks,
Ted.

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Trellis graphics and clipping

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