uicontrol question: Slider only acts on last Figure, does not act on Figure it's associated with.

MATLAB version: R2012b

I'm trying to learn uicontrol using the example given from http://www.mathworks.com/help/matlab/ref/uicontrol.html

I put the example into a for loop running 3 times and get 3 plots.

Question 1: I get Figure1, Figure2, & Figure5. Why Figure5? Why does it skip 3 & 4?

Question 2: The pop-up menu and the push button both control the plot the buttons are on (which is the action I'm wanting) but the sliders on all 3 plots only controls the last plot made (i.e., Figure5).

Restating - the pop-up menu & push button on Figure1 will control the Figure1 plot, and likewise for Figure 2 & 5, but the slider on Figure1 controls the Figure 5 plot, and likewise the slider on Figure2.

I want the slider to behave like the pop-up and push button and control the Figure they're placed on. I thought perhaps that ax needed to be a matrix referenced to ii, i.e., ax(ii) but that didn't help. Note that when I looped it twice (and only have a Figure1 & Figure2) I have the same issue.

Here's the code:

 function myui

 for ii = 1:3

    % Create a figure and axes
    f = figure('Visible','off');
    ax = axes('Units','pixels');
    surf(peaks)

    % Create pop-up menu
    popup = uicontrol('Style', 'popup',...
           'String', {'parula','jet','hsv','hot','cool','gray'},...
           'Position', [20 340 100 50],...
           'Callback', @setmap);   

   % Create push button
    btn = uicontrol('Style', 'pushbutton', 'String', 'Clear',...
        'Position', [20 20 50 20],...
        'Callback', 'cla');       

   % Create slider
    sld = uicontrol('Style', 'slider',...
        'Min',1,'Max',50,'Value',41,...
        'Position', [400 20 120 20],...
        'Callback', @surfzlim); 
          
    % Add a text uicontrol to label the slider.
    txt = uicontrol('Style','text',...
        'Position',[400 45 120 20],...
        'String','Vertical Exaggeration');

    % Make figure visble after adding all components
    set(f,'Visible','on');

 end %end for ii    

    function setmap(source,callbackdata) 
                    % source = handle to the object that was used to call the function
                    % callbackdata is the event associated with the object.
        val = get(source,'Value');
        maps = get(source,'String'); 
        newmap = maps{val};
        colormap(newmap);
    end

    function surfzlim(source,callbackdata)
        val = 51 - get(source,'Value');
        zlim(ax,[-val val]);
    end

end %end function myui

Answer 1

[Geoff Hayes]

Tom - I'm not sure why you see figures 1, 2, and 5 as when I run the code, I see figures 1 through 3. Perhaps you have two figures, 3 and 4, already open? Add following line to the beginning of your script which will close all open figures.

 close all;

As for the sliders being applied to the last figure only, look closely at the code. On each iteration of the for loop you assign the following to the local variable ax

 ax = axes('Units','pixels');

That means on the third iteration of the loop, ax will be the axes for the third figure. Now look at the slider callback

 function surfzlim(source,callbackdata)
     val = 51 - get(source,'Value');
     zlim(ax,[-val val]);
 end

We reference the local variable ax which is the axes to the third figure and since you are using the same callback for each slider, then all changes to the slider will be applied to the third axes only.

We need to somehow indicate which axes each slider should be applied to and we do this by passing the axes handle as an input into the slider callback. For example,

 % Create slider
 sld = uicontrol('Style', 'slider',...
                 'Min',1,'Max',50,'Value',41,...
                 'Position', [400 20 120 20],...
                 'Callback', {@surfzlim,ax});

Note how we pass ax as an input into the callback. Now define the callback as

 function surfzlim(source,callbackdata,hAxes)
     val = 51 - get(source,'Value');
     zlim(hAxes,[-val val]);
 end

We define hAxes as the third input to the callback (the first two inputs are the default input parameters) and use it in the call to zlim.

Try integrating the above into your code and see what happens!

[Thrashercharged]

Geoff - thanks for your clearly written response! I thought the problem had to do with ax being assigned to the last figure after all iterations but I tried to address that by making ax a matrix ax(ii) in both the main script and surfzlim function. However I did not pass ii through as an input to the function but I'm still not sure if making ax a matrix is a workable approach. Regardless, your method is better.

The use of the 2 default inputs for uicontrol still puzzles me as to what they exactly do. I assume they just have to be there?

Also, I'm still not clear how the popup menu only alters the Figure it's assigned to. No inputs (except for those 2 defaults) are being passed between the main script and the setmap function. I understand the default input "source" is the handle to the object that was used to call the function, so does that mean "source" = "popup"? But every Figure created by each iteration of the loop would be named the same then, so how does it "know" which Figure to act on?

As I mentioned, this is merely the example script given in the uicontrol docs but I'm trying to understand it as I need to do a similar thing using uicontrol in my scripts. Thanks for your help!

[Geoff Hayes]

The use of the 2 default inputs for uicontrol still puzzles me as to what they exactly do. I assume they just have to be there?

I'm pretty sure that the first two inputs to this callback (and others) are typical/expected. As per the comments from your other callback

 % source - handle to the object that was used to call the function
 % callbackdata - is the event associated with the object.

callbackdata (usually?) is just an empty matrix but for callbacks that support key events, this would contain (for example) information about the key pressed. source is the handle to the object that the callback function is assigned to (and allows you to use the get and set property functions). There are always exceptions to this so I can't say for sure that all callback will have at least these two inputs (though I suspect that this is true).

I understand the default input "source" is the handle to the object that was used to call the function, so does that mean "source" = "popup"?

The source parameter is the handle (or unique identifier) to (in this case) the popup menu uicontrol that has been created for the figure. Depending upon your version of MATLAB, this is either a double scalar (so something like 132.4343) or a structure/object (at least R2015a). So each control will have a different/unique handle associated with it.

Also, I'm still not clear how the popup menu only alters the Figure it's assigned to.

When you select an element from the popup menu, you are bringing focus to that uicontrol and to the figure itself. So now the figure (whose popup menu is being modified) is the current figure which the colormap will be set for. (So in this case, there is no need to explicitly pass an input handle for the figure or axes to modify as this happens implicitly when you select the control of the figure.)

Answer 2

[Walter Roberson]

Prevent confusion. Always "Parent" your graphics operations. See http://uk.mathworks.com/matlabcentral/answers/22208-show-figure