Re: Gnuplot and Octave.

[Ole J. H. <wat...@ya...>]

Hi, again.

I know Octave can get some parameters from gnuplot using gshow, which 
will run show in Gnuplot.
And a lot of types, parameters and properties related to current plot is 
available here.
All these could be collected from Octave.

There is a lot of builtin functionality inside gnuplot to be used within 
Octave, and could be interpreted as handle graphics.
Remark that gnuplot doesn't have to support a core handle graphics. 
Handle graphics of Matlab is very restrictive,
and should be interpreted as some sort of Mathworks attempt to 
generalize properties of a visualisation.

Gnuplot should continue in it's development regardless of handle graphics.

The question is whether Gnuplot is doing some housekeeping of curve-data 
(2D & 3D), and this is retrievable in an easy way.

It would be nice to be able to retrieve the curve_data which is 
visualised. That would be perfect.

I know that Octave is able to use a gshow, which will list out 
properties as in show.  
I believe I can get labels, ticks, colour and format, but not the 
curve_data, which could be quite useful....


Cheers

Ole J.




Daniel J Sebald wrote:

>
>
> Hans-Bernhard Broeker wrote:
>
>> On Fri, 20 Feb 2004, Ole Jacob Hagen wrote:
>>
>>  
>>
>>> Gnuplot has visualisation properties, which could be interpreted, and
>>> used by Octave by our package. But, there is always a but. We need to
>>> make duplicate copies of datasets, which are plotted in Gnuplot, since
>>> Gnuplot doesnt send it's dataset of visualisation back.
>>>   
>>
>>
>> I don't think I see what that "dataset of visualization" you're talking
>> about is.
>>
>> Anyway: is this about 3D or 2D plots?  Or colour maps?
>>
>>  
>>
>>> This is the curve/surface data, such as X, Y and Z.
>>>   
>>
>>
>> How would these differ from the data sent from octave to gnuplot?
>>
>
> Probably most on this list are familiar with Matlab's handle graphics 
> objects, but just in case I'll summarize.  Matlab extends the concept 
> of matrices to the plot realm by associating elements of a plot to an 
> elements in a vector.  Think of these elements as "handles".  Using 
> "get" will get the vector of handles associated with a particular 
> figure.  For example, here is a short segment of code to change the 
> line width of a plot:
>
>  H = get(get(gcf,'Children'),'Children');
>  set(H(1),'LineWidth',2.0);
>
> You'll notice to use of "get" twice.  The reason is that there is a 
> hierarchy of plot elements.  For example, an axis will be an element, 
> and then under that will be other elements for the axis like text. 
> "get" alone without assignment will display all the information about 
> a handle object such as the actual text, the font type, the size of 
> the font, etc.  The sub-objects are called children.
>
> Naturally, this requires a storing of all information about the plot 
> elements.  Or, it requires some way of inquiring such information from 
> Gnuplot, if Gnuplot keeps a record of such things.  A plot line is 
> also an object and part of its characteristics is all the data points 
> associated with it.  So, this is what the original question is about. 
> Is it possible to get back the (x,y,z) information that Petr is 
> referring to from Gnuplot.
>
> A few things:
>
> 1)  This would mean that somehow information about plot data would 
> need to be sent back to Octave through the pipe so that Octave could 
> interpret it and use it in a handle graphics fashion.  I'm not sure if 
> Gnuplot is set up to do such a thing.
>
> 2)  It would then seem that to do this would require the strategy 
> that, I think it was, Hans has mentioned about each Gnuplot plot 
> storing all information so that it can be retrieved.  (I assume same 
> goes for all other elements like labels, etc.)  From Gnuplot's 
> perspective, this was for allowing the mouse to zoom on not only the 
> most recent plot, but all plots in X11.  But here would be an example 
> of another use.
>
> 3)  I don't know what Ole has in mind, but I assume that this concept 
> has to be extended to all other graph objects, i.e., labels and so on. 
> That is, either Gnuplot is the one to keep track of all the 
> retrievable information, or Octave is the one.
>
> You may be wondering, how does one know what the hierarchy is Matlab? 
> That is, how did I know to use "get" twice in the above script example 
> and then select element H(1) from the array of handle objects?  Well, 
> one has to simply display the information, following the hierarchy of 
> children down to the object of interest.  It isn't the most apparent 
> logic as to how things are grouped, but perhaps once you get used to 
> it, things become easier.
>
> However, I'm going to give my experience about this, and keep in mind 
> that this is opinion.  (Repeat OPINION!)  I was exposed to Matlab 
> before Octave so the handle object approach is what I first used to 
> customize plots.  I never found it easy to use; quite arduous 
> actually.  The searching through children of children of children part 
> is what gets to one after while.  Switching over to Octave, I found 
> that using "gset" and the Gnuplot customizing commands a bit easier to 
> use.  The handle graphics approach is to create the graphics objects 
> and then go back and modify them (going through the handle hierarchy 
> in the process).  The Gnuplot approach is to set the object property 
> at the same time the object is created, and be done with it.  In 
> Gnuplot, setting a default property is often very easy as well.
>
> I could say more here, but I will leave it open for further comment 
> from others.
>
> Dan
>
>
>
>
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