MATLAB: Command ‘plot3’ clears functions which were added when an axes is created in GUIDE. Why

axesbuttondownfcnguiplot3r2016b

Hi all,

I created an axes – My_Axes (using GUIDE but I think it doesn't matter) – and specified a 'ButtonDownFcn' to treat mouse clicks on the created graph. However, when I plot something on this axes using the the funcition 'plot3' the axes field 'ButtonDownFcn' is cleared! Of course, nothing happens when later I click with the mouse on the graph. Strangely, this is not the case when I create a graph using 'plot' (I didn't check all the other plotting functions). Why? Is this the way Matlab is suppose to treat axes?

Thanks,

Alon

Best Answer

I don't believe this is a bug. When you call a high-level plotting function like plot or plot3, MATLAB needs to know how to configure the axes into which the graphics object will be plotted. By default, "new plots added to the axes clear existing plots and reset all axes properties." [That's not technically true; the Position and Units properties keep their values.]

To avoid this behavior, use the hold function to change the behavior from the default behavior I described above, use a lower-level plotting function like line, or manually change the axes NextPlot property (which is similar or equivalent to what hold does.)

I'm guessing you didn't see this behavior when you called plot because you also used hold or because you set the ButtonDownFcn property after plotting.

Related Solutions

MATLAB: Is the ‘ButtonDownFcn’ property of an axes in a GUI not called after I plot a figure in MATLAB 7.3 (R2006b)

High-level plotting functions, by default, clear the axes properties (except the 'position' and the 'units' property).

To prevent calls to PLOT, BAR, etc. from replacing the buttondownfcn, set the 'NextPlot' property of the axes to 'replacechildren' instead of the default 'replace'. This will clear the axes contents and plot the new data without replacing the axes object itself.

If you want to plot data over your existing data, then set the 'NextPlot' property of the axes to 'Add'.

An alternative workaround is to assign 'ButtonDownFcn' for the axes again after calling the plot.

function test()
% Creating dummy data 'a' and 'b'
   a=3;
   b=4;
   h=figure;
   plot(rand(3));
   axes_handle = gca;
   set(axes_handle, 'ButtonDownFcn', {@FcnName,a,b}); 
function FcnName(src,evnt,a,b)
    disp('click down!!!')
    disp(a)
    disp(b)

MATLAB: Axes tag disappears after imagesc

The difference in behavior is due to the different value of the NextPlot property between axes and uiaxes.

Most graphics commands (including plot and imagesc) call a helper function called newplot. This command is designed to "prepare a figure and axes for subsequent graphics commands." It does this by checking the value of the NextPlot property on the axes:

If NextPlot is 'replace' the newplot command will reset the axes back to its default state (resetting all properties, including the Tag). This is the default value for regular axes (created with the axes command).
If NextPlot is 'replacechildren' the newplot command will delete the children of the axes, but won't reset any properties (so the Tag is preserved). This is the default value for uiaxes.
If NextPlot is 'add' the newplot command will not modify the axes or delete the children. When you turn hold on, the hold command sets the NextPlot property to 'add'.

In response to your comment about "in some operations I need to get the axis handle to do something".

My recommendation is to try to store the handle to your axes and reuse that, rather than relying on something like findobj (which I assume is how you are searching for the axes with your tag). You are already doing that in several places in your code. For example, you are already passing your axes handle into your callback function (plotButtonPushed) so you do not need to rely on the tag. This is the general approach I would recommend.

If that doesn't work, then you will either need to change the NextPlot value (either directly or using hold) before you call plot or imagesc, or reset the Tag after every call to a plotting function.

Best Answer

Related Solutions

MATLAB: Is the ‘ButtonDownFcn’ property of an axes in a GUI not called after I plot a figure in MATLAB 7.3 (R2006b)

MATLAB: Axes tag disappears after imagesc

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