Semilogy and zeros

[Marco Caliari]

Dear John,

your patch was not applied to Octave 3.2.2.

Best regards,

Marco

On Thu, 16 Jul 2009, John W. Eaton wrote:

> On 16-Jul-2009, Ben Abbott wrote:
>
> | On Jul 16, 2009, at 6:42 AM, Marco Caliari wrote:
> |
> | > Dear maintainers,
> | >
> | > the following command
> | >
> | > semilogy([1e-16,0],'*')
> | >
> | > produces the warning
> | > warning: axis: omitting nonpositive data in log plot
> | >
> | > and the corresponding plot in Octave 3.0.5, but an empty plot in
> | > Octave 3.2.0. I think the old behaviour is the right one. I'm using
> | > Gnuplot 4.2.5.
> | >
> | > Best regards,
> | >
> | > Marco
> |
> | I don't see this warning in the m-file sources.
>
> It comes from a function in graphics.cc.
>
> | However, I have reproduced Marco's examples.
>
> I checked in the following change.  It seems to fix the problem for
> me.
>
>  http://hg.savannah.gnu.org/hgweb/octave/rev/ac2617d4e30c
>
> Note that the axis calcuation for log scale plots is still not quite
> right when we have to discard negative data.  Currently, for example,
> we discard the data for plotting, but we compute the axis limits
> independently, on the full data.  Instead, I think we need to discard
> the skipped data, then compute the axis limits.  But this seems like a
> minor point, and will also require some significant restructuring, so
> I have no plans to fix it.  However, I would consider a patch.
>
> jwe
>