[R] Where are the ticks on grid.xaxis?

[David A. Johnston]

Hi R list,

I like the default ticks that are set up using grid.xaxis() or grid.yaxis()
with no arguments.  Finding good values for the 'at' argument is usually not
a trivial task; the default behavior of these functions seems to work well. 
The problem with this strategy is that I cannot figure out how to "recover"
the positions of these ticks when you do NOT specify the 'at' argument.  

For example:

grid.newpage()
pushViewport(plotViewport(c(5, 4, 2, 2), name = "myvp"))
# This draws a default xaxis
a = grid.xaxis(name = "myX")
# What are the tick marks?
grid.get("myX")$at  # NULL

# But if I specify an 'at' argument...
grid.edit("myX", at = seq(0, 1, length = 10))
# ...I can get at the position of the ticks
grid.get("myX")$at

Is it possible to find the tick positions created by grid.xaxis() or
grid.yaxis() if no 'at' parameter is specified?

Thanks,

-David Johnston

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