Re: gnuplot and dashed lines

[Daniel J Sebald]

On 12/20/2012 07:39 PM, Ben Abbott wrote:
> On Dec 20, 2012, at 10:55 AM, Ben Abbott wrote:
>
> > On Dec 20, 2012, at 10:46 AM, CdeMills wrote:
> >
> > > Hello,
> > >
> > > I was struggling to obtain dashed lines without success. At first I believe
> > > it was MacOs specific; now I've found the problem.
> > >
> > > If you take the content of
> > > http://gnuplot.sourceforge.net/demo/dashcolor.html
> > > and paste it into gnuplot interface, you get the same figure as given on the
> > > web page. If you download the script provided at
> > > http://gnuplot.sourceforge.net/demo/dashcolor.1.gnu which is supposed to
> > > give exactly the same result, you don't.
> > >
> > > There is a subtle difference: the script does not include the 'set
> > > termoption dashed' command at the beginning. This makes a lot of
> > > differences: by default, it seems that gnuplot renders all lines as solid.
> > >
> > > To verify, it tried this simple script:
> > > x = 1:10;
> > > h=plot (x,x,'-;line 1;',x,x+1,'--;line 2;')
> > >
> > > I got a figure with two continuous lines. Then I did
> > > drawnow("aqua", "/dev/null", false, "debug.gp")
> > > edited the debug.gp file, added a "set term option dashed" at the beginning,
> > > then, in a terminal:
> > > gnuplot<  debug.gp
> > >
> > > and got the dashed lines ! The missing point is thus to add this
> > > "termoption" at the beginning of the gnuplot script. Another option is to
> > > create a "~/.gnuplot" with this line:
> > > set termoption dashed
> > >
> > > Restarted Octave, ran the same script, and got a dashed line directly!
> > > Dash-dot working too.
> > >
> > > This should be either corrected into the gnuplot interface, either
> > > documented. Moreover, gnuplot seems to not have a way to query the
> > > termoption settings. I don't see how to interactively test wether or not
> > > this feature is supported.
> > >
> > > Regards
> > >
> > > Pascal
> >
> > If you are intetested in making a changeset, the place for this change is in 
> > __gnuplot_drawnow__.m, or in __go_draw_figure__.m
> >
> > Ben
>
> I'm not sure if the "dashed" option can be used in all terminals, but I tried 
> the change below.

Generally no, but now days the most used of the terminals should 
supported dashed lines.  In gnuplot that dashed-line-support quirk is a 
bit of a throwback.

It's odd though that this should just surface now without others 
noticing a fairly common feature missing from plotting in Octave.  I'm 
going to check with the gnuplot list on this.


> diff --git a/scripts/plot/__gnuplot_drawnow__.m 
> b/scripts/plot/__gnuplot_drawnow__.m
> --- a/scripts/plot/__gnuplot_drawnow__.m
> +++ b/scripts/plot/__gnuplot_drawnow__.m
> @@ -321,6 +321,14 @@
>           endif
>         endif
>       endif
> +    dashed_terms = {"aqua", "cairolatex", "canvas", "cgm", "context", ...
> +                    "eepic", "emf", "epslatex", "fig", "pcl5", "tikz", ...
> +                    "mp", "next", "openstep", "pdf", "pdfcairo", ...
> +                    "pngcairo", "postscript", "pslatex", "pstex", ...
> +                    "svg", "tgif", "windows", "wxt", "x11"};
> +    if (any (strncmp (term, dashed_terms, numel (term))))
> +      fprintf (plot_stream, "set termoption dashed\n")
> +    endif
>     else
>       ## gnuplot will pick up the GNUTERM environment variable itself
>       ## so no need to set the terminal type if not also setting the
>
> "aqua" produced a dashed line, but neither qt (no "dashed" option) or x11 did.

I've tried a rather recent version of gnuplot here.  Qt terminal seems 
to support dashed lines (introduced on 2011-12-14), but not X11.  Try:

gnuplot> set term qt
Terminal type set to 'qt'
Options are '0'
gnuplot> test
[no dashed lines in the right column]
gnuplot> set termoptions dashed
gnuplot> test
[dashed lines in right column]
gnuplot> set term x11
Terminal type set to 'x11'
Options are ' nopersist'
gnuplot> test
[no dashed lines]
gnuplot> set term x11 dashed
Terminal type set to 'x11'
Options are ' nopersist dashed'
gnuplot> test
[no dashed lines...doesn't seem right]
gnuplot> set termoptions dashed
gnuplot> test
[no dashed lines...expected give previous result]

The dashed terminal test might not be necessary.  I think (but not sure) 
that the "set termoption <opt>" is supposed to be a universal type of 
setting and terminals are supposed to check that.


> Apparently more work will be needed to support the linestyles for x11.

I will look into this.  I just tried the latest gnuplot and the "test" 
plot is a mess in X11.

Dan