[R] Titles changing when a plot is redrawn

[John Nolan]

Thank you for telling me a fix.  

But I still don't know if this behavior is what is intended.  I used bquote(...) because the plotmath(...) help page refers to bquote and gives an example like this.  I suspect most users will be baffled by this kind of behavior, especially since it does not occur when there is one plot.  By this I mean that I can draw one plot and title it with the same string using bquote( ).  If I change the value of i, and redraw the graph, the redrawn graph has the original value of i in the title, not the updated value. So in this case, an unevaluated expression is not re-evaluated at draw time?

John 


-----xieyihui at gmail.com wrote: -----
To: John Nolan <jpnolan at american.edu>
From: Yihui Xie 
Sent by: xieyihui at gmail.com
Date: 10/05/2011 11:49PM
Cc: r-help at r-project.org
Subject: Re: [R] Titles changing when a plot is redrawn

I think the problem is your str1 is an unevaluated expression and will
change with the value of i. You should be able to get a fixed title by
this:

par(mfrow = c(2, 1))
for (i in 1:2) {
    x <- 1:100
    rmse <- sin(x/5)  # fake data
    plot(x, rmse, main = substitute(list(RMSE(theta), i == z), list(z = i)))
}

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
Phone: 515-294-2465 Web: http://yihui.name
Department of Statistics, Iowa State University
2215 Snedecor Hall, Ames, IA



On Wed, Oct 5, 2011 at 10:01 PM, John Nolan <jpnolan at american.edu> wrote:
> 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 )
> }
> #-------------------------------------------------
>
>
>  ...........................................................................
>
>  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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