R-beta: error in x11 graphics?

Albrecht Gebhardt (albrecht.gebhardt@uni-klu.ac.at)
Tue, 21 Jul 1998 21:00:45 +0200 (CEST)

Date: Tue, 21 Jul 1998 21:00:45 +0200 (CEST)
From: Albrecht Gebhardt <albrecht.gebhardt@uni-klu.ac.at>
To: r-help@stat.math.ethz.ch
Subject: R-beta: error in x11 graphics?

Hi,

please could somebody try the following lines:

x<-c(-808996808,-820483729)
y<-c(1429449991,372653377)
xrange<-c(-824726000,-820002315)
yrange<-c(369266958,373990642)

# only one point should appear because the other lays outside the plot ranges:
plot(x,y,xlim=xrange,ylim=yrange)

# this should produce a line directed to the hidden point
lines(x,y)

If it would work correct, you should get something like this:

+---------------+
| / |
| o |
| |
| |
| |
+---------------+

But my R (0.62.2 on Linux) produces a line downwards, and if I rescale
the plot, it changes its direction from downwards to right and to upwards.

Whats the matter?

May be a rounding error in the X11 code?

Postscript versions of this plot are ok: I tried the plot commands from above with

postscript("/tmp/test1.ps",horizontal=F,height=7,width=7)
postscript("/tmp/test2.ps",horizontal=F,height=7,width=3)
postscript("/tmp/test3.ps",horizontal=F,height=3,width=7)

and all looked like my sketch above.

Of course, the ratio between the ylim dimensions of the plot and the
distance in y-direction between the two points is very small (0.004),
but why should it work with postscript only?

Albrecht

------------------------------------------------------------------------------
Albrecht Gebhardt email: albrecht.gebhardt@uni-klu.ac.at
Institut fuer Mathematik Tel. : (++43 463) 2700/837
Universitaet Klagenfurt Fax : (++43 463) 2700/834
Villacher Str. 161 WWW : http://www-stat.uni-klu.ac.at/~agebhard
A-9020 Klagenfurt, Austria
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