Re: gnuplot-4.4.0-rc1 breaks gnuplot script

[Teo S B. <teo...@gm...>]

On Fri, Feb 12, 2010 at 7:07 PM, Ethan Merritt <merritt@u.washington.edu>wrote:

> On Friday 12 February 2010 09:58:45 Teo S Bernhard wrote:
> > Problem:
> > Gnuplot script that set parameter repeatedly in plot command to address
> the
> > data index (within a data file) does not work when using gnuplot version
> > 4.4.0-rc1.
> > It works in 4.2 version and, from memory, did also work in version 4.3.
> See
> > the below shortened example reproducing the error message:
> >
> >
> > # file: trial.gpl
> > f(x)=x
> > plot a=1, \
> >      f(x)*a   title "data from index a=1" w l lw 2 lt a ,  a=a+1,       \
> >      f(x)*a   title "data from index a=2" w l lw 2 lt a ,  a=a+1,       \
> >      a=0
>
> Please see Bug #2907028
>
> https://sourceforge.net/tracker/?func=detail&aid=2907028&group_id=2055&atid=102055
>
> So far as I can tell from running old versions of gnuplot (back to 3.7),
> it never did work correctly to increment a variable multiple times inside
> a plot command.
>
>
Test of referred bug report:
I have tested and it is is reproducible. There is however a subtle
difference with my example and that  of the bug report. Note that I initiate
the counter variable first in the plot command. Then - the problem vanish.
The parameter incrementation is then correct!
You can convince yourself by trying the following:

k=0
plot [0:1] [-1:]             k=0,   \
    k*x t '0x'  w lp lt 1,   k=k+1, \
    k*x t '1x' w lp  lt 2,   k=k+1, \
    k*x t '2x' w lp  lt 3

Now, if you remove the initial 'k=0, \' part of the plot-command - the
'0x'-line is plotted as 2*x, the '1x'-line as 3*x and '2x'-line as 4*x. Can
this be related to the two 'k=k+1' for some strange reason? In deed, adding
a third 'k=k+1' leads the first '0x'-line to be plotted as 3*x!  This is
clearly a bug since k is expected as zero for the first line to be plotted,
'0x'.

I therefore think there are two issues here:
1) The issue reported as Bug #2907028 and
2) the issue reported by me here, that version 4.4 does not allow an
increment as the last statement of a plot-command.

This test on Ubuntu 8.04, gnuplot 4.2 patchlevel  2 and  gnuplot 4.3
patchlevel  0.

> pause -1 "Continue?"
> >
> > #
> > # gnuplot 4.2 patchlevel 5 accepts the above. I believe that also
> > # gnuplot 4.3 accepted this.
> > #
> > # gnuplot-4.4.0 patchlevel 0-rc1 give error:
> > #    "trial.gpl", line 6: function to plot expected
> > #
> > #
> > #  It works if I add a dummy curve after a=0, so that last line
> > #  becomes:
> > #                   a=0, x/0
> > #
> > exit
> >
> > Best regards
> > Teo
> >
>
>