[Rd] Bug with png() and plot(type="n") (PR#7270)

[Peter Dalgaard]

mcintosh at research.telcordia.com writes:

> Full_Name: Allen McIntosh
> Version: 2.0.0
> OS: Linux
> Submission from: (NULL) (67.80.175.118)
> 
> 
> Observed the bug with the following combinations: (RedHat 7.3, R 1.6.0) (RedHat
> 7.3, R 1.9.1) (Redhat 9, R2.0.0).
> 
> In the second plot (.png file) produced by the following sequence:
> 
> png(file="x%d.png")
> plot(1:10,1:10,main="ooo",type="n")
> segments(1:9,1:9,2:10,1:9)
> plot(1:10,10:1,main="XXXX",type="n")
> 
> the axis labels, the tick marks and the title from the first plot have not been
> erased.  The call to segments() seems to be necessary, as does type="n".  The
> example I extracted this from also called abline(), which was sufficient to
> trigger the bug.  Inserting a call to frame() after the call to segments()
> results in an extra file that ought to be blank, but instead contains the
> offending text and tick marks.
> 
> Workarounds short of multiple calls to png() appreciated.

Apparently, the clipping of segments is still active when the drawing
surface is erased.

Inserting a call to box() before the 2nd plot seems to help. 

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907