postscript failure manifests in plot.TukeyHSD

On 16/12/10 04:24 AM, "Paul Murrell" <p.murrell at auckland.ac.nz> wrote:

Hi

According to the PostScript Language Reference Manual and the PDF
Reference, in both PDF and PostScript ...

... a line width of zero is valid, but not recommended (and is clearly
not supported by some viewers).

... a line dash pattern cannot be specified as all zero lengths.
(So, because R generates the line dash pattern proportional to the line
width, a specification of lwd=0 and
lty=anything-other-than-"solid"-or-"none" does not make sense.)

I think three fixes are required:

(i)  Enforce a minimum line width of 0.01 (mainly because that is not
zero, but also because that is the smallest value greater than zero when
you round to 2dp like the PDF and PostScript devices do and it's still
REALLY thin).

(ii) If the line dash pattern ends up as all zeroes (to 2dp), because
the line width is so small (thin), force the dash pattern to "solid"
instead.

(iii) plot.TukeyHSD() should not use lwd=0  (0.5 is plenty difference to
be obviously "lighter" than the main plot lines)

I will commit these unless there are better suggestions or bitter
objections.

Paul,

The difference between working previous (of R 2.11.1) and failing
current-still-yesterday (R 2.12.1 RC) was:

$ diff -U2 oldtukeyplot.ps /Volumes/TIKKU/tukeyplot.ps
--- oldtukeyplot.ps    2010-12-14 12:06:07.000000000 +0200
+++ /Volumes/TIKKU/tukeyplot.ps    2010-12-14 12:13:32.000000000 +0200
@@ -172,5 +172,5 @@
 0 setgray
 0.00 setlinewidth
-[ 3.00 5.00] 0 setdash
+[ 0.00 0.00] 0 setdash
 np
 660.06 91.44 m

So 0.00 setlinewidth worked, but [0.00 0.00] 0 setdash failed. Assuming
PostScript is anything like English, it is the all-zero dash that caused the
failure. 

Cheers, Jari Oksanen