@Yair,

Using struct may not be the optimal solution; I, personally, prefer your ^[14] utility due to its graphical and interactive interface. One must not forget your instrumental ^[15] and ^[16] utilities for inspecting java objects.

On another matter: the data cursors in HG2 have TeX interpretation capabilities. It had been a default option in the non-official HG2 releases (Matlab R2013b with “-hgVersion 2” startup); however, it has been removed in the official Matlab R2014b release. Using the uiinspect function, I found the Interpreter residing in the TipHandle property of DataCursor. To re-enable it use simply:

hDataCursorMode = datacursormode();
hDataCursor     = hDataCursorMode.createDatatip(someTargetHandle);
hDataCursor.TipHandle.Interpreter = 'tex';
hDataCursorMode.Enable = 'off'; % turn off

If one wishes to use just the interactive data cursors, they can simply change the UpdateFcn of the data cursor mode:

hDataCursorMode.UpdateFcn = @myUpdateFcn;
...
function txt = myUpdateFcn(obj,evd)
obj.TipHandle.Interpreter = 'tex';
txt = sprintf('\tau = %g\n\mu_i = %g',evd.Position(1),evd.Position(2));
end

It is such a simple and useful feature; I wish that TMW made it documented and accessible…

These days, I typically use the metaclass function for this kind of thing.

>> metaclass(hContour)
ans = 
  GraphicsMetaClass with properties:

                     Name: 'matlab.graphics.chart.primitive.Contour'
              Description: ''
      DetailedDescription: ''
                   Hidden: 0
                   Sealed: 1
                 Abstract: 0
              Enumeration: 0
          ConstructOnLoad: 1
         HandleCompatible: 1
          InferiorClasses: {0x1 cell}
        ContainingPackage: [1x1 meta.package]
             PropertyList: [178x1 meta.property]
               MethodList: [129x1 meta.method]
                EventList: [13x1 meta.event]
    EnumerationMemberList: [0x1 meta.EnumeratedValue]
           SuperclassList: [6x1 matlab.graphics.internal.GraphicsMetaClass]

That list of properties in PropertyList includes 178 of the 181 properties that you found with struct (the missing ones apparently being “SerializableChildren”, “SerializableUIContextMenu”, and “TopLevelSerializedObject”). Using metaclass won’t give you GetAccess to properties which deny it like struct does, but at least for base MATLAB graphics classes, the list of properties with private or protected GetAccess is usually very small and properties that you probably don’t need anyway (that contour object has 6 properties with protected GetAccess: “SerializableApplicationData”, “SerializableBehavior”, “CreateFcn_IS”, “DeleteFcn_IS”, “ButtonDownFcn_IS”, and “SerializableUserData”).

The benefits of using the metaclass function are that it gives you access to a lot more information: property attributes (Hidden, GetAccess, etc), methods (including hidden ones), and even pointers to the meta.class objects of superclasses inherited by the object in question.

@Greg – thanks for mentioning metaclass, which indeed complements struct. In my eyes, the main benefit of struct is not in its access to private/protected properties (as you’ve noted, these are probably of little or no interest), but rather in providing the current values of each of the properties. It is very convenient to scan a list of property/values to find something that looks interesting – much easier than to scan through the internal lists exposed by metaclass. The property value help me understand the nature of the property, which is not always clear from its name. Had MathWorks programmers taken the time to document properties and classes using their internal Description metaproperty, this could be different. But unfortunately, the vast majority of descriptions are either empty or contain the boilerplate ‘TODO: Fill in Description’ string.

I often need to get the x position of each bar in a grouped bar plot so I can put errorbars on them. With HG1, I would get the x position of the ith bar with:

hBar = bar(randn(5));
x = get(get(hBar(i), 'Children'), 'XData');
x = x(2, 🙂 + diff(x(2:3, :))/2;

With HG2, I have to use the undocumented XOffset property which I found with your struct method.

hBar = bar(randn(5));
x = get(hBar(i), 'XData') + get(hBar(i), 'XOffset');

Interestingly, and I don’t know if it is a general HG2 bug, but the undocumented XOffset property does not initially get set correctly if the NextPlot property of the axes object is set to Add:

figure;
set(gca, 'NextPlot', 'Add')
hBar = bar(randn(5));
get(hBar(1), 'XOffset')
drawnow;
get(hBar(1), 'XOffset')

Here’s another usage example of using the bars’ undocumented XOffset property to get the bar centers for the benefit of the errorbar function: ^[17]

Hello,

I am trying to follow your example of grabbing the brushed data. Before I continue, I’m not really good with Matlab so I apologize if I am a bit slow to follow. Anyways, when I make a simple plot and try

handle = hPlot.BrushHandles;

I get an error saying ‘No appropriate method.’ After some quick google searching, I see that the error message may be related to accessing a nonpublic property and I tried

handle = hPlot.get('BrushHandles');

Then I get ‘There is no BrushHandles property on the Figure class.’

So I checked the properties using struct(hPlot) and I’ve combed through and can’t seem to find anything related to brush data. Is there something obvious that I am missing? I am using version 2015a.

@Yow-Ren – your hPlot variable is not a plot handle (returned from the plot function) but a figure handle, so of course it doesn’t work…

Yair, do you know if any of these TriangleStrips properties controls transparency (similar to the FaceAlpha property)?

Thanks,

Nick Gianopoulos

@Nick – I do not understand your question: at the very top of this post I showed how to use the ColorType and ColorData properties of the TriangleStrip objects in order to achieve transparency.

@Yair – So you did, I just failed to read the first part of this post for some reason. Lol, I’m honestly in shock over how quick your reply was – thanks so much! It’s been one of those days … Huge fan of your work btw

Hi,

extracting the x-coordinates (on R2016a, Linux) using

hLine.XData(logical(hLine.BrushData))

works fine with data plotted using plot(), but if I use scatter() instead, the extracted x-coordinates do not match the brushed ones. This seems somehow unexpected to me…

Best,
Christoph

addition: the problem only appears when using log-scaling on the y-axis and the y-data contains zeros. Minimal working example:

h = scatter(1:5, [0 1 0 2 0]);
set(gca(), 'YScale', 'log')

now brush some data-point and try

h.XData(logical(h.BrushData))

The zeros still appear in h.YData and h.BrushData is of same size, however, its indexing seems different (considering visible symbols only).

@Christoph – I believe that this is due to an internal Matlab bug. You can try to report this to MathWorks but don’t be too hopeful, since this functionality is undocumented/unsupported after all…

@Yair – I found that the bug also affects the “official way”: brushing data and selecting Tools->Brushing->Create new variable… also gives the wrong result.
One can also observe it visually in my example above, when switching between linear and logarithmic scaling: the brushed points change!

@Christoph – excellent: this means that you can report this to MathWorks as an official bug. If and when you ever learn anything new about this, then please update with a new comment here.

update: MathWorks confirmed that the observed behaviour is indeed a bug affecting MATLAB R2014b through MATLAB R2016a (Technical Support Case #01981712). Their developers are working on fixing this issue.

update: the issue is fixed in R2016b. The position of flags in h.BrushData now corresponds to data-points in h.XData and h.YData (irrespective of data-point visibility due to log-scaling)

Thanks for the update, Christoph

Hi,I programed callbacks for brush mode operations below,which I wanted to access the point I brushed. However,it don’t work. Can you tell me where I am wrong? Thanks!

t=0:0.2:25; 
plot(t,sin(t),'.-');
h=brush;
set(h,'Enable','on','ActionPostCallback',@displaybrushdata);

function displaybrushdata(src,~)
   brushedIdx = logical(src.BrushData);
   brushedXData = src.XData(brushedIdx);
   brushedYData = src.YData(brushedIdx);
   disp('ok');
end

Hi Yair,
There is “VertexData” in property of “TriangleStrip .FacePrims”, but there is no information about patch “faces” that can connect vertices to each other.
Is there any way to use from VertexData and extract border or relationship between triangles of one region?

Yair, I found the solution by using “hFills(i).StripData”. Thanks