Do you ever make use of non-uniform arrays of structures?

Loren explained in the following comment on her blog that certain vectorized struct assignment syntax is not currently allowed because there is no guarantee that arrays of structs are uniform: http://blogs.mathworks.com/loren/2007/04/19/vectorizing-access-to-an-array-of-structures/#comment-16189

She proposes adding a new 'uniform' struct data type to permit this. Personally I'd rather enable the syntax for existing structs and error if one tries the syntax on a non-uniform array of structs, because I've never had the need to use non-uniform struct arrays as a data structure in my programming. Have you?

Answer 1

[Jan]

Yes, I use non-uniform structs. For a motion analysis I store different measurements in a struct array and some of the measurements contain an EMG measurement, and some don't. But of course, I do not try to apply a vectorized access to the subfields (because this would fail). So I agree that allowing this kind of access for the current structs should be valid, when for non-uniform data an error is thrown.

Answer 2

[Sean de Wolski]

When you save a figure, it is internally stored as a *.mat file containing a scalar structure.

If you dig into this for a fancy figure, there can many instances of non-uniformity amongst the various children and their properties (since the children are not necessarily the same class). E.g:

S = load('complicatedFigure.mat'); %rename from complicatedFigure.fig
S.hgS_070000.children.children.properties

As for me: never used 'em.

[Eric Sampson]

Sean, I thought an array has to be non-scalar in order to have the potential to be non-uniform. In other words, no scalar array can be non-uniform by definition (unless it contains a nested struct array, but would you then call the parent a scalar structure? :)

[Sean de Wolski]

The parent is the scalar structure with n fields:

S.hgS_070000

ans =

          type: 'figure'
        handle: 1
    properties: [1x1 struct]
      children: [1x1 struct]
       special: []

Now digging into children, which is also scalar:

S.hgS_070000.children

ans =

          type: 'axes'
        handle: 174.0011
    properties: [1x1 struct]
      children: [4x1 struct]
       special: [4x1 double]

We see the non-scalar ones come out of the woodwork. Now, digging into the children's properties (which are different classes!), we see the non-uniformity:

S.hgS_070000.children.children.properties

ans =

              CData: [49x49 double]
          EdgeColor: [0 0 0]
              XData: [49x49 double]
              YData: [49x49 double]
              ZData: [49x49 double]
    ApplicationData: [1x1 struct]
          XDataMode: 'manual'
        XDataSource: ''
          YDataMode: 'manual'
        YDataSource: ''
          CDataMode: 'auto'
        CDataSource: ''
        ZDataSource: ''

ans =

                  Units: 'data'
              FontUnits: 'points'
        BackgroundColor: 'none'
                  Color: [0 0 0]
            DisplayName: ''
              EdgeColor: 'none'
              EraseMode: 'normal'
                DVIMode: 'auto'
              FontAngle: 'normal'
               FontName: 'Helvetica'
               FontSize: 10
             FontWeight: 'normal'
    HorizontalAlignment: 'left'
              LineStyle: '-'
              LineWidth: 0.5000
                 Margin: 2
               Position: [-27.6849 -38.6747 53.3734]
               Rotation: 0
                 String: 'x'
            Interpreter: 'tex'
      VerticalAlignment: 'top'
          ButtonDownFcn: []
              CreateFcn: []
              DeleteFcn: []
             BusyAction: 'queue'
       HandleVisibility: 'off'
           HelpTopicKey: ''
                HitTest: 'on'
          Interruptible: 'on'
     SelectionHighlight: 'on'
           Serializable: 'on'
                    Tag: ''
               UserData: []
        ApplicationData: [1x1 struct]
                Visible: 'on'
            XLimInclude: 'on'
            YLimInclude: 'on'
            ZLimInclude: 'on'
            CLimInclude: 'on'
            ALimInclude: 'on'
        IncludeRenderer: 'on'
               Clipping: 'off'
       i_CachedPosition: [-27.6849 -38.6747 53.3734]

ans =

                  Units: 'data'
              FontUnits: 'points'
        BackgroundColor: 'none'
                  Color: [0 0 0]
            DisplayName: ''
              EdgeColor: 'none'
              EraseMode: 'normal'
                DVIMode: 'auto'
              FontAngle: 'normal'
               FontName: 'Helvetica'
               FontSize: 10
             FontWeight: 'normal'
    HorizontalAlignment: 'right'
              LineStyle: '-'
              LineWidth: 0.5000
                 Margin: 2
               Position: [-30.8417 -36.1657 53.6635]
               Rotation: 0
                 String: 'y'
            Interpreter: 'tex'
      VerticalAlignment: 'top'
          ButtonDownFcn: []
              CreateFcn: []
              DeleteFcn: []
             BusyAction: 'queue'
       HandleVisibility: 'off'
           HelpTopicKey: ''
                HitTest: 'on'
          Interruptible: 'on'
     SelectionHighlight: 'on'
           Serializable: 'on'
                    Tag: ''
               UserData: []
        ApplicationData: [1x1 struct]
                Visible: 'on'
            XLimInclude: 'on'
            YLimInclude: 'on'
            ZLimInclude: 'on'
            CLimInclude: 'on'
            ALimInclude: 'on'
        IncludeRenderer: 'on'
               Clipping: 'off'
       i_CachedPosition: [-30.8417 -36.1657 53.6635]