hexbin and grid - input data values as coordinates

Hi
Dear all,

I am trying to use hexbin and read the very interesting article on grid
( http://www.ci.tuwien.ac.at/Conferences/useR-2004/Keynotes/Murrell.pdf ) and am hoping for some advice from more experienced users of hexbin.

I am trying to visualise a data and fit a straight line trough it. For
example, here is how I would do it in the usual way

 # simulate data  
 x <- rnorm(1000)
 y <- 5*x + rnorm(1000, sd=0.5) 

 plot( x, y, pch="*" )
 abline(0, 1, col=2)

And here is my failed attempt at fitting the "abline" on hexbin

 library(hexbin); library(grid)
 plot( hexbin( x, y ), style = "nested.lattice") 
 grid.move.to(0.2,0.2)
 grid.line.to(0.8,0.8)

I realise that grid.* is taking plotting coordinates on the graph but
how do I tell it to use the coordinates based on the data values ? For
my real data, I would like lines with different slopes and intercepts.
gplot.hexbin() returns the viewports it used to produce the plot and the 
legend.  Here's an example of annotating the plot ...

  # capture the viewports returned
  vps <- plot( hexbin( x, y ), style = "nested.lattice")
  # push the viewport corresponding to the plot
  # this is actually a hexViewport rather than a plain grid viewport
  # so you use pushHexport rather than grid's pushViewport
  pushHexport(vps$plot.vp)
  # use "native" coordinates to draw relative to the axis scales
  grid.move.to(-2, -10, default.units="native")
  grid.line.to(2, 10, default.units="native",
               gp=gpar(col="yellow", lwd=3))
  # tidy up
  popViewport()

There's another annotation example at the bottom of the help page for 
gplot.hexbin

A grid.abline() function would obviously be a useful addition.  Must 
find where I put my todo list ...

Paul
I am using the hexbin version 1.2-0 ( which is the devel version ),
R-2.0.1 and Fedora Core 3.

Many thanks in advance.

Regards, Adai

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hexbin and grid - input data values as coordinates

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