Re: segfault in plot3d

[Ethan A M. <merritt@u.washington.edu>]

On Wednesday 18 February 2009, Daniel J Sebald wrote:
> James R. Van Zandt wrote:
> 
> > Daniel J Sebald <dan...@ie...> wrote:
> > 
> >>That explains it.  The double line break means to start another 3D
> >>curve.  (A single break means to start another trace of the 3D curve.)
> >>So Jim's example is attempting a 3D plot with single dimensioned data.
> > 
> > 
> > I don't follow what you mean by "single dimensioned data".  Each point
> > has an X, Y, and Z value.  With "set style data lines", the points are
> > connected along only one dimension, which is fine with me.  Actually I
> > was using the default style, so I got only the points.
> > 
> > 
> >>Either a check should be put in plot3d.c, or a datafile [like this]
> >>should be disallowed...
> > 
> > 
> > I see no reason to disallow it.  It used to work.  And it still works
> > unless you plot data after a function.  (Succeeds by accident?)
> 
> Good chance, would be my guess.  Someone disallowed the number of samples in a dimension to be 1.
> 
> 
> > The docs say
> > 
> > "If all datablocks contain the same number of points, gnuplot will
> > draw cross-isolines between datablocks, connecting corresponding
> > points."
> > 
> > Apparently gnuplot should check that there is more than one datablock
> > before attempting to draw cross-isolines.
> 
> Yes.
> 
> Philosophically, I'm not opposed to having a single line of data appear in a 3D plot.  It's probably the case that 3D plotting functions expect (i.e., assume, or, were never tested) there to be some type of grid.
> 

You're over-thinking this.  There is nothing to stop you from plotting a series
of points in 3D that have nothing to do with a surface.  The problem data file
happens to contain 4 sets of such points.  If you split it into four separate
files, it works as expected
   splot 'line1', 'line2', 'line3', 'line4', x+y

What has gone wrong (I eventually realized) is that the code added for iteration
assumes that if you generated multiple curves from the same input file it is
_because of iteration_, whereas in this case it is simply because the input file
contains more than one curve.  I will fix that.


-- 
Ethan A Merritt