Re: plot templates and options lists for set, plot etc.

[Ben Abbott]

On Jun 6, 2009, at 11:21 AM, Thorsten Meyer wrote:

> Hi,
>
> at work, I often have to generate the same kind of plots with  
> particular labels,
> line styles, etc.. I would like to create templates for these plots.  
> For this, I
> collect plot options in a struct like it is returned by the get  
> function. E.g.
>  style = struct("linewidth", 2, "marker", "x", "markersize", 12);
>
> Now, I want to pass these options to the plot function. At the  
> moment, I do it
> like this:
>  plot(1:5, 5:-1:1, {fieldnames(style)'{:}; struct2cell(style)'{:}} 
> {:});
>
> Or:
>  h=plot(1:5, 5:-1:1);
>  set(h, {fieldnames(style)'{:}; struct2cell(style)'{:}}{:});
>
> Does anyone know a more elegant way of converting a structure to a  
> cs-list of
> key, value, ...?
>
> Also, I would like to wrap this transformation into a function. I  
> tried it like
> this (in octave compiled from the current tip):
>
> function varargout = struct2options (structure)
>  varargout = {fieldnames(structure)'{:}; struct2cell(structure)'{:}};
>  nargout
> endfunction
>
> And, indeed, the function works in a way:
>  [a, b, c, d] = struct2options(style)
>  ans = 4
>  a = linewidth
>  b =  2
>  c = marker
>  d = x
>
> However, used within a plot command, the following happens:
> octave:177> plot(1:5, 5:-1:1, struct2options(style))
> ans =  1
> error: plot: properties must appear followed by a value
> error: called from:
> error:   /home/thorsten/local/share/octave/3.1.55/m/plot/__plt__.m  
> at line 62,
> column 8
>
> Apparently, in that context, the function struct2options settles on  
> delivering
> only one return argument.
> Is there any way to force a function to deliver all its output  
> arguments? I
> tried to set nargout within the function but that didn't change  
> anything.
>
> Apart from that, whouldn't it be good to extend the syntax of the  
> plot functions
> (or at least the set function) such that they also accept options in a
> structure? Then, the above commands could also be:
>  plot(1:5, 5:-1:1, style)
> respectively
>  h = plot(...)
>  set(h, style)
>
> regards
>
> Thorsten

Would you prefer the approach below?

        props = {"color", [0 1 0], "marker", "s"}
        h = plot (1:10);
        set (h, props{:})

If you want to continue to use your structure, you can populate props  
by ...

        props = [fieldnames(style), struct2cell(style)];

But that is not really very different from what you're already doing.

Ben