HG’s undocumented parameters interface

6 Responses to HG’s undocumented parameters interface

1. Eric says:

   March 14, 2013 at 8:13 am

   Is this behavior because the functions use INPUTPARSER? If so, perhaps it is true for any function that uses inputparser – I haven’t tested it out to see…

   Reply
   • Yair Altman says:

     March 14, 2013 at 8:17 am

     @Eric – both line, patch and inputparser are internal functions whose contents are not accessible for us to check.

2. Pingback: ishghandle’s undocumented input parameter | Undocumented Matlab

3. Miguel Gaspar says:

   April 4, 2013 at 12:25 pm

   I had also noticed this sometime ago. It would seem very useful to use with:

   hprops=get(h);
   hprops.some_property=...
   set(h,hprops)

   but unfortunately get(h) returns read-only properties, which result in an error when used with set():

   >> set(hl,linep)
   ??? Error using ==> set
   Attempt to modify a property that is read-only.
   Object Name :  line
   Property Name :  'Annotation'.
   

   Do you know how to overcome this?

   Reply
   • Yair Altman says:

     April 4, 2013 at 2:30 pm

     @Miguel – why not simply pass to set only the changed properties, that you can be certain are settable? For example:

     hprops = [];
     hprops.some_property1 = ...
     hprops.some_property2 = ...
     set(h,hprops)
   • Miguel Gaspar says:

     April 4, 2013 at 3:38 pm

     Hi, Yair,

     Thanks for your reply, and above all, thanks for the continuous stream of pearls you provide…

     I would like to use the get() method for two reasons:
     – symmetry: it has some aesthetic appeal, feels natural to me;
     – laziness: it would allow the use of auto-complete…

     not very strong reasons, specially since recent versions of Matlab provide auto-complete of property names in set/get, but still prompted me to write this function:

     function hprops=getset(h)
     % Returns only the settable properties for the handle graphics object h, so
     % that it can be used directly in the form:
     % set(h,hprops)
      
     fn=fieldnames(set(h(1)));
     fv=get(h,fn);
     hprops=cell2struct(fv',fn,1);

     Unfortunately, although this works for a vector of handles, of same type, returning a vector struct, this can’t be used in set(...):

     hlines=findobj(gca,'Type','line');
     lineprops=getset(hlines);
     lineprops(1).LineStyle=':';
     lineprops(2).LineStyle='-';
     set(hlines,lineprops)

     since only the last value specified for each property is used, and applied to all handle graphics objects…

     A syntax for assigning different values to properties of multiple objects is available for the plot(...) function, which accepts the following:

     plot(1:4, [2,4,5,8], 'r',...
          1:4, [3 2 1 4], 'g')

     My preferred way of working with handle graphics is to use hg objects instead of handles, although in some cases it requires some additional steps:

     hline=hg.line('XData',1:4,'YData',[2,4,5,8]);
     hline.Visible=false;
     hline.XData=[hline.XData,5];
     hline.YData=[hline.YData,3];
     hline.Visible=true;
     % or:
     [hline.XData,hline.YData]=deal([hline.XData,5],[hline.YData,3]);

     Which method (set(…) with PV pairs, set(…) with struct, or hg objects) do you prefer?