HG's undocumented parameters interface

6 Responses

1. 
   Eric March 14, 2013 at 08:13 Reply

   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…

• 
  Yair Altman March 14, 2013 at 08:17 Reply

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

2. ishghandle’s undocumented input parameter | Undocumented Matlab March 27, 2013 at 14:09 Reply

   […] Two weeks ago I wrote about Matlab Handle Graphics (HG) undocumented acceptance of structs as input parameter to some plotting functions. Continuing in a related matter, today I expose an undocumented input parameter for HG’s ishghandle function […]

3. 
   Miguel Gaspar April 4, 2013 at 12:25 Reply

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

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

   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?

• 
  Yair Altman April 4, 2013 at 14:30 Reply

  @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)

  hprops = []; hprops.some_property1 = ... hprops.some_property2 = ... set(h,hprops)

• 
  Miguel Gaspar April 4, 2013 at 15:38

  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);

  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)

  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')

  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]);

  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?

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<pre lang="matlab">
a = magic(3);
disp(sum(a))
</pre>

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