Re: postscript dash patterns in parametric vs data plots

[Mojca M. <moj...@gm...>]

2010/3/30 Jonathan Thornburg wrote:
> Hi, all,
>
> On Mon, 29 Mar 2010, Hans-Bernhard Br?ker wrote:
>> I'll venture a guess, then: the difference disappears if you use the same
>> number of points for both lines, right?  I.e. if you 'set samples 2' for (a),
>> the two plots will be the same.  Or if you output the sampled function to a
>> data file (--> help table), and plot that in place of the inline data, the two
>> plots will again be the same.
>
> Success!  I've experimented with placing 'set samples N' for various N
> near the start of my test gnuplot script, with the following results
> (this is still using gnuplot 4.2.6 on my computer; I've just downloaded
> gnuplot-4.4.0.tar.gz but haven't compiled/installed it yet):
>        N       result
>        1000    wierd dash pattern for parametric line
>        300     wierd dash pattern for parametric line
>        200     wierd dash pattern for parametric line
>        150     almost-normal dash pattern for parametric line
>                (very slightly different from that for explicit-data
>                 line when viewed at high magnification)
>        100     normal dash pattern for parametric line
>        2       normal dash pattern for parametric line
>
> Moreover, this now explains the apparent system-dependence (i.e.,
> Ethan not being able to reproduce the problem): my personal
>  $HOME/.gnuplot   file contains (among other things) 'set samples 1000'.
>
> Question:  Ethan, do you see the wierd dash patterns (or even the
> same eps file as I do?) if you put 'set samples 1000' at the start
> of my gnuplot script?

Oh, nice observation. At 104-105-106 gnuplot (or maybe PS terminal)
most probably starts being a bit more "careful" about too long lines.

with 'set samples 104':

1 0 V
2 0 V
2 0 V
% End plot #1
% Begin plot #2
stroke

with 'set samples 105':

1 0 V
2 0 V
2 0 V
stroke 1137 882 M
% End plot #1
% Begin plot #2
stroke

with 'set samples 106':

2 0 V
1 0 V
2 0 V
stroke 1135 882 M
2 0 V
% End plot #1
% Begin plot #2
stroke

At least the example with 'set samples 105' seems very weird to me.

Mojca

(PS: one could definitely optimize the output with zillions of lines like
2 0 V
2 0 V
1 0 V
2 0 V
1 0 V
2 0 V
1 0 V
2 0 V
2 0 V
)