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Re: st: problems with gridlines in Stata 8.2 graphs


From   vwiggins@stata.com (Vince Wiggins, StataCorp)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: problems with gridlines in Stata 8.2 graphs
Date   Mon, 24 Nov 2003 13:20:34 -0600

Matthew Sydes <Matthew.Sydes@ctu.mrc.ac.uk> reports the same problem reported
by Michael Blasnik <michael.blasnik@verizon.net> last week -- twoway graphs
with multiple X- or Y-axes sometimes overlay gridlines on top of the plotted
lines or markers.  I cannot currently reproduce this on my machine ..., but
then that is only because the problem has already been fixed in my version of
Stata.  This fix will be available in the next ado update, but because there
are some things for the update that are not yet complete, we don't expect the
update to be available until early next week.

I have to admit that Matthew and Michael got caught in what was a bit of an
experiment.  We knew this was possible when Stata 8 shipped, but in all of the
cases we could conjure the graphs were rather complicated and we thought
unlikely.  Matthew's last example produced the problem with a relatively
simple graph and in a way we had not anticipated.

Not that Matthew or Michael are probably much interested, but the problem
stemmed from a very elegant algorithm wherein graph objects draw themselves
with no knowledge of the overall graph structure or other objects.
Unfortunately, multiple axes lead to multiple, overlayed plotregions, and
since it is the plotregions that hold both the grids and the plots (lines or
markers) this leads to the grids from one plotregion potentially occulting the
plots from another region.

Suffice to say that we have sacrificed some hidden elegance for the practical
matter of drawing what people expect.  

 
-- Vince
   vwiggins@stata.com

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