[Octave-bug-tracker] [bug #56798] semilogy - "omitting non-positive data in log plot" and empty plot with all positive data

[Andrea Baldoni]

Follow-up Comment #6, bug #56798 (project octave):


[comment #5 comment #5:]
> Given some randomly generated data on my end, I get the same warning and I
get a valid plot with both 4.0.3 and 5.1.0. In other words, the warning is not
tied to an empty plot, in either version. There does not seem to be a bug here
with the information you have given.

I discovered the problem. The data I am plotting, is composed by isolated
non-zero values, surrounded by zero values.
As semilogy discards zero data, it doesn't plot anything at all (it doesn't
join the remaining non-zero data with lines as I expected, neither it plot
dots, unless you use "marker", ".").

I don't know if it's a bug or a "feature".
If you wish to check it on other versions (my linux distribution has only the
4.0.3 available) or graphics toolkits, this is a simple demo:

clear;
a=[0.5, 0, 2, 0, 0.01, 0, 4, 0, 0.1, 0, 3, 0, 0.002];
graphics_toolkit('gnuplot');
figure(1, 'position',[0,0,1200,300]);
subplot(1,3,1);
semilogy(1:13, a);
subplot(1,3,2);
semilogy(1:13, a, "marker", ".");
subplot(1,3,3);
semilogy(1:13, a+10^-10);
pause;


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