MATLAB generating a ghost figure

I have a UI for brushing and labeling data. I've included a simplified version of the script below. The problem is that MATLAB is randomly generating a blank figure in addition to the GUI every time I run it. If I remove the "hold on; plot(DETECTIONS{i}, 'rx'); hold off" line and the "brush on" line, this extra figure is not generated. However, including either the hold on or the brush on portions causes MATLAB to generate a blank figure despite it never being explicitly asked to in the code. Any thoughts about why this could be happening and how to avoid it?

% initialize GUI
nplot = 4; % number of subplots
fig = uifigure('name', 'Label Detections');
grd = uigridlayout(fig, [nplot, 1]);
for i = 1:nplot
     uipan(i) = uipanel(grd);
     ax(i) = uiaxes(uipan(i));
end

% Find GUI figure, plot data on it
fig = findall(0, 'Type', 'figure', 'name', 'Label Detections')
for i = 1:nplot
    plot(ax(i), DATA{i})
    hold on
    plot(ax(i), DETECTIONS{i}, 'rx')
    hold off
end

brush on

Answer 1

[Cris LaPierre]

You also need to specify the target axes/figure for your calls to hold and brush

You should probably be using a uifigure instead of figure. At least I get a warning that some of the functionality is not supported in figures.

Try this (untested)

hold(ax(i),'on') % and 'off'
brush(fig,'on')

[Eric Snyder]

Thanks!

The line fig = figure is a typo and should be fig = uifigure. I edited the original question.

The hold(ax(i),'on') does the trick for the hold, but adding brush(fig, 'on') doesn't seem to actually activate the brush. I can always go in and click the brush icon, but it would save a bit of time and usability to have it already activated when the user runs the program.

[Cris LaPierre]

I have never used this option before, so you may not have to do anything with this one. Check out the description of the various syntaxes at the top of the documentation page if you still get a ghost figure after reverting this to just brush on.

[Eric Snyder]

I'm accepting the answer, because as you and Walter Roberson both mentioned, hold on and brush on were the lines generating a new figure, since MATLAB looks for a figure, not a uifigure, when those commands are called. I'm still trying to figure out how to get the brush to activate for uiaxes, but since that's a separate question I think I'll post that elsewhere. Thanks!

[Walter Roberson]

I had no problem activing brush on a uiaxes

brush(ax(i), 'on')

[Eric Snyder]

I replaced uiaxes with axesand it now works just fine. I'm not sure what the problem was prior. It's possible a setting I had somewhere else in my code didn't get along with uiaxes, but as of now I haven't figured out why it gave me trouble.

Answer 2

[Walter Roberson]

fig = figure('name', 'Label Detections');

That creates a "traditional figure"

grd = uigridlayout(fig, [nplot, 1]);

uigridlayout() cannot be children of traditional figures.

     ax(i) = uiaxes(uipan(i));

uiaxes() cannot be children of traditional figures.

         hold on

When you do not pass a parent to hold then it looks for the current axes, and creates a current axes if need be, which might involve creating a current figure. Only traditional axes (and traditional figures) are examined: the default never looks for uiaxes or uifigure.

You would need

         hold(ax(i), 'on')

[Eric Snyder]

Oops, that's a typo. It should be uifigure, not figure. I edited the question. Thanks

[Walter Roberson]

Anyhow, hold on and brush on are your problems.