How can I prevent a function from creating a separate window when acting on a UIfigure handle?

I have a script that reads in some data and a UI figure with uibuttons that change how it is plotted. I've stripped the non-essential parts that don't relate to the issue out of the code. This SHOULD create a UI window that has 2 UI slider elements and a push putton that reads the current value of the sliders and uses that to plot data in the same figure to an axes inside the window on the right created by UIaxes. It will plot the data as intended, BUT it also creates a new figure window with a blank axes in it when the "update" button is pressed. How do i get it to stop doing this? If the plot() function is called outside of a local function it will plot to the correct axes, but I need it to be inside the update function so that it can replot when UI elements are changed.

% some mock data to make the simplified code run
raw_spectra.ampl = [1 2 3];
raw_spectra.field = [1 2 3];


% make the uifigure and axes
fig = uifigure("Position", [50, 300, 1200, 900]);

Error using matlab.internal.lang.capability.Capability.require
This functionality is not available on remote platforms.

Error in matlab.ui.internal.uifigureImpl (line 32)
Capability.require(Capability.WebWindow);

Error in uifigure (line 26)
window = matlab.ui.internal.uifigureImpl(varargin{:});

ax = uiaxes(fig,'Position',[350, 40, 820, 820]);

% make an element in the uifigure that adjusts a parameter that affects how
% plotting is done.
fig.UserData.horizStagger = uislider(fig,"Limits",[0 7],"Position",[30, 250, 200 3],...
        'Value', 0);
fig.UserData.vertStagger = uislider(fig,"Limits",[0 3],"Position",[30, 170, 200 3],...
        'Value', 0.5);

% a ui button element that when pushed, plots or replots the data with the 
% parameters selected with the other UI elements
update_btn = uibutton(fig, 'push', 'Position', [130, 450, 125, 22], ...
    'Text', 'Update', 'ButtonPushedFcn', ...
    @(update_btn, event) update(update_btn, fig, raw_spectra));

function update ( ~, fig, raw_spectra)        
    
    staggeredSpectra = stagger(raw_spectra, fig.UserData.horizStagger.Value, ...
        fig.UserData.vertStagger.Value);
    
       
    for i =1:numel(staggeredSpectra)
        plot(fig.Children(end), staggeredSpectra(i).field, ...
            staggeredSpectra(i).ampl);
        hold on;
    end
    hold off;
end

function spectra  = stagger (input_spectra, horizStagger, vertStagger)
    for s = 1:numel(input_spectra)
        %adjust center so that that maxima line up with staggering added for
        %horizontal offset 

   
        spectra(s).field = input_spectra(s).field + horizStagger;

        %scale relative to the largest spectrum height and apply vertical
        %offset
        spectra(s).ampl = input_spectra(s).ampl * vertStagger * (s-1);

    end
end

[dpb]

Because you're plotting to the figure, not updating the axes. See the uibutton <example callback> that draws into an axes on being pushed.

IOW, you need to create your axes, then update the data in it, not address the figure with a plotting command; that's what creates the new axes in the figure.

[Andrew Morris]

In the example link you gave, the code is written with the plot() function inside the callback function, with the axes supplied as an argument to the callback function, which is what you say I shouldn't do. should I be doing like:

fig = uifigure;
ax = uiaxes(fig);

button = uibutton (fig, 'push', 'ButtonPushedFcn', ...
    @(src, event) update(ax, raw_spectra));

function update (ax, raw_spectra)
    ax.Children.xData = raw_spectra.field;
    ax.Children.yData = raw_spectra.ampl;

end

    

[Voss]

@Andrew Morris: Have you tried the modification given in my answer? I ran it, and it worked (version R2022a).

[Andrew Morris]

yes! thank you. it requires making the plot first in this way outside of a function and then using the update callback to swap out the ax.Children.XData and ax.Children.YData vectors in place without using the plot function.

Answer 1

[Voss]

It's because of the

hold on

without specifying an axes.

Specify the axes explicitly, e.g.:

hold(fig.Children(end),'on');

Similarly for the hold off a couple lines later.