gnuplot-beta

Re: segfault in plot3d

[James R. V. Z. <jr...@co...>]

Ethan A Merritt <merritt@u.washington.edu> writes:
>Why does your data file have two blank lines between each set of points?
>
>If you reduce that to a single blank line then there is no segfault.
>Of course, it should not segfault in any case, but I'm wondering if
>this is why no one has reported the problem before.

I used two blank lines so I could use "index" specs to select portions
of the data file for plotting, or more usefully, for fitting.

From: Daniel J Sebald <dan...@ie...>
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 "James R. Van Zandt" <jr...@co...>
Subject: Re: segfault in plot3d
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Ethan A Merritt wrote:

>>gnuplot> splot 'lin2.dat',x+y
> 
> 
> Why does your data file have two blank lines between each set of points?
> 
> If you reduce that to a single blank line then there is no segfault.
> Of course, it should not segfault in any case, but I'm wondering if
> this is why no one has reported the problem before.

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?)  

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.

          - Jim Van Zandt

Re: segfault in plot3d

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

On Wednesday 18 February 2009 09:36:12 James R. Van Zandt wrote:
> 
> Ethan A Merritt <merritt@u.washington.edu> writes:
> >Why does your data file have two blank lines between each set of points?
> >
> >If you reduce that to a single blank line then there is no segfault.
> >Of course, it should not segfault in any case, but I'm wondering if
> >this is why no one has reported the problem before.
> 
> I used two blank lines so I could use "index" specs to select portions
> of the data file for plotting, or more usefully, for fitting.

That's fine.  I was just wondering if there was a quick work-around available.

I have figured out why the iteration tracking is interfering with the
multiple-data-sets-per-file case, but still have to think about how best
to fix it.



> 
> From: Daniel J Sebald <dan...@ie...>
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> To: Ethan A Merritt <merritt@u.washington.edu>
> CC:  gnu...@li..., 
>  "James R. Van Zandt" <jr...@co...>
> Subject: Re: segfault in plot3d
> References: <E1L...@va...> <200902172152.08953.merritt@u.washington.edu>
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> 
> Ethan A Merritt wrote:
> 
> >>gnuplot> splot 'lin2.dat',x+y
> > 
> > 
> > Why does your data file have two blank lines between each set of points?
> > 
> > If you reduce that to a single blank line then there is no segfault.
> > Of course, it should not segfault in any case, but I'm wondering if
> > this is why no one has reported the problem before.
> 
> 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?)  
> 
> 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.
> 
>           - Jim Van Zandt
> 
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742

Re: segfault in plot3d

[Daniel J S. <dan...@ie...>]

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.

Dan

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