Re: Plans for gnuplot version 5 [per-line ranges]

[Tait <gnu...@t4...>]

> > I think I remember some discussion a while back about changing plot's
> > syntax to specify a per-line range for plots. Something akin to:
> >   set xrange [-10:10]
> >   plot [0:10] sqrt(x), [-10:0] -log(-x+1)
> > 
> > ... as a substitute for the current approach:
> >   rangefunc(x,min,max,func)=(x>min)&&(x<=max) ? func : 1/0
> >   plot rangefunc(x,0,10,sqrt(x)), rangefunc(x,-10,0,-log(-x+1))
> > 
> > Did that idea ever go anywhere? 
> 
> A variant of this went into CVS more than a year ago.
> 
>    http://gnuplot.sourceforge.net/demo_cvs/piecewise.html

Okay sorry, I forgot that and didn't find it within the archives I
still have handy.

> > Since it's backward-incompatible with the current plot [] syntax, it would
> > probably have to be a major version change.
> 
> In what way is it incompatible? 
> I don't recall seeing any reports of breakage.

In the current versions (4.6p3 or p5), the initial []-enclosed values
are taken as the overall x- and y- range.
  plot [5:11][3:12] x, x/2+4
is equivalent to
  set xrange [5:11]; set yrange [3:12]; plot x, x/2+4
and a range like [7:9] before the x/2+4 is a syntax error.

Changing this as outlined above (and apparently as-implemented in
CVS?) is incompatible because now the [3:12] above would be a syntax
error* and the [5:11] would apply only to the x and not to the x/2+4
line, and the overall plot x-range is still presumably at its previous
setting, or default [-10:10].


* maybe? I suppose gnuplot could implement a per-line y-range by
calculating the point it would draw, then not drawing it if it falls
outside the y-range given for that line.