[R] Titles changing when a plot is redrawn

[John Nolan]

I ran into a problem with titles on graphs.  I wanted a graph with
multiple subplots, with each having a title that involved both
a Greek letter and an identifier for each graph.  Below is a 
simplified version of code to do this.  The graph appears fine,
with the first graph having "i=1" in the title, and the second
graph having "i=2" in the title.  However, when I resize the graph, 
the plot titles change, with both showing "i=2". The titles also
change when I save the plot to a file using the "File" menu,
then "Save as" in Windows.  Is this what should happen?  I
always thought that titles are static once the graph is 
drawn, and couldn't change.

The problem occurs on some version of R, but not on others.
It does occur with the latest version of R:
> str(R.Version())
List of 13
 $ platform      : chr "i386-pc-mingw32"
 $ arch          : chr "i386"
 $ os            : chr "mingw32"
 $ system        : chr "i386, mingw32"
 $ status        : chr ""
 $ major         : chr "2"
 $ minor         : chr "13.2"
 $ year          : chr "2011"
 $ month         : chr "09"
 $ day           : chr "30"
 $ svn rev       : chr "57111"
 $ language      : chr "R"
 $ version.string: chr "R version 2.13.2 (2011-09-30)"

The problem also occurs on:  R 2.13.0 on Win32
  and Mac (R 2.12.0, x86_64-apple-darwin9.8.0)
The problem DOES NOT occur under R 2.10.0 on Win32.

If the code below is bracketed with pdf("test.pdf")
and dev.off(), the correct labels appear in the file.
This behavior doesn't seem to appear if there is only
one plot.

My guess is that the titles are being reevaluated when
the plot is redrawn, and since the value of i is 2 when
the redraw occurs, both labels get set to "i=2".  I guess
"Save as" forces a redraw because a dialog box pops up?

If could be that this behavior is what is intended, and that 
somewhere between R 2.10.0 and R 2.13.2 an old bug was fixed.  
Or this behavior is not what was intended, and a bug was 
introduced.  If the former, this should be explained to the user 
somewhere.  If the latter, can someone track it down and fix?

John Nolan

#-------------------------------------------------
par(mfrow=c(2,1))
for (i in 1:2) {
  x <- 1:100
  rmse <- sin(x/5)  # fake data
  plot(x,rmse)
  str1 <- bquote( paste("RMSE(",theta,"), ",i==.(i)  ))
  title( str1 )
}
#-------------------------------------------------


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 John P. Nolan
 Math/Stat Department
 227 Gray Hall
 American University
 4400 Massachusetts Avenue, NW
 Washington, DC 20016-8050

 jpnolan at american.edu
 202.885.3140 voice
 202.885.3155 fax
 http://academic2.american.edu/~jpnolan
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