Re: Legend help

[Quentin Spencer]

John W. Eaton wrote:
> On  7-Nov-2006, Dmitri A. Sergatskov wrote:
>
> | Since we are on the subject.
> | 
> | The current version of legend fails if called before the first invocation of
> | gnuplot:
> | 
> | octave:1> legend("junk1")
> | error: invalid row index = 0
> | error: evaluating argument list element number 1
> | error: evaluating argument list element number 1
> | error: evaluating prefix operator `!' near line 208, column 7
> | error: if: error evaluating conditional expression
> | error: evaluating if command near line 208, column 3
> | error: called from `legend' in file `/arch1/dima/incoming/legend.m'
> | octave:1> plot(rand(5))
> | octave:2> legend("junk1")
> | 
> | (works now)
> | 
> | octave:3>
> | 
> | I do not think it is a very serious problem, but want to let you know...
>
> I just checked in a largeish patch that fixes this problem and adds
> legend.m to Octave (it should probably be removed from Octave Forge
> now).  Instead of the error above, you should see
>
>   octave:1> legend ("boxon")
>   octave:2> legend ("foo", "bar")
>   warning: legend: plot data is empty; setting key labels has no effect
>
> The "boxon" setting will affect subsequent plots.  Setting key labels
> with legend should happen after plotting data.
>
> Instead of trying to extract the current key labels by saving the
> current plot state and parsing the output with awk, Octave now saves
> the key labels in a structure and uses that to add labels to the plot
> as needed.  The legend function now just modifies the data structure.
> As this change is relatively invasive, it would be good if people
> could do some testing with the current plot code in Octave's CVS
> archive.
>   

I think this is the right approach for the legend function. I've removed 
the old legend.m function from octave-forge, and I've done some testing 
of the new one. The first thing I noticed is that it doesn't seem to be 
marked as command. Doesn't the

## PKG_ADD mark_as_command legend

in legend.m make it automatically marked at octave startup? I'm not sure 
why it's not working for me. Here's another thing I noticed--this was 
probably the case before, but all the same it would be nice to fix. In 
addition to storing the legend strings, attributes like position and use 
of box should be stored, so that the following code results in the 
legend being in the upper left with a box:

octave:1> plot(rand(10,2));
octave:2> legend('test1','test2',2);
octave:3> legend('boxon');
octave:4> legend('hide');
octave:5> legend('show');

Otherwise, I think it works pretty well. Also, if we're interested in 
having the same default settings as Matlab (not that I care much in this 
case), the default is 'boxon'.

Quentin