Wandering usr values in par(no.readonly=TRUE) (PR#2283)

[maechler@stat.math.ethz.ch]

>>>>> "Marc" == Marc Schwartz <mschwartz@medanalytics.com>
>>>>>     on Wed, 13 Nov 2002 11:01:49 -0600 writes:

    Marc> Marc Schwartz wrote:
    >>  SNIP
    >> 
    >> I am guessing that this may be the result of par("ylog")
    >> and par("xlog") being read only and perhaps impacting the
    >> restoration of the par("usr") values when the plotting
    >> device is still open, but that may be incorrect.

    Marc> In follow up to my own note from last evening on this
    Marc> and now that I have had a couple of cups of coffee
    Marc> this morning, I need to partially correct my above
    Marc> statement and point to a presumed typo in the ?par
    Marc> help file.  For confirmation, this is R 1.6.1 under
    Marc> WinXP Pro.

    Marc> par("xlog") and par("ylog") are not Read Only
    Marc> parameters as listed in the help file and can be set
    Marc> by the user.  Indeed this is confirmed in the comments
    Marc> in par.r:

    Marc> #.Pars.readonly <- c("cin","cra","csi","cxy","din")

    Marc> I noted this today as I was comparing the output of
    Marc> par() with par(no.readonly = TRUE) and noted that the
    Marc> latter returns '$xlog' and $ylog' as being
    Marc> settable. The other 5 par values listed in ?par as
    Marc> "R.O." (cin, cra, csi, cxy and din) return errors when
    Marc> one attempts to set them with par(args), however xlog
    Marc> and ylog do not.

Yes, indeed, and I -- as an R-core member -- am astonished:.
I didn't know it really worked, but it does, e.g., 

  > plot(1:10); par("usr")
  [1]  0.64 10.36  0.64 10.36
  > par(xlog = TRUE); par(c("xlog","usr"))
  $xlog
  [1] TRUE

  $usr
  [1] -0.1938200  1.0153598  0.6400000 10.3600000

  > points(10^(1:9), 1 + 1:9, col = "red") # draws red points above 


I'm now re-directing this back to R-bugs to make sure that 
the only (right?) remaining bug, documentation in par.Rd, 
will be fixed -- and hope to close this as a bug report.

    Marc>   ..........
    Marc>   <more good analysis>

Thank you Marc!

Martin Maechler <maechler@stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO C16	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><

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