Automatically Refresh Plot in a GUIDE App

Note

The GUIDE environment will be removed in a future release. After GUIDE is removed, existing GUIDE apps will continue to run in MATLAB^® but they will not be editable in GUIDE.

To continue editing an existing GUIDE app, see GUIDE Migration Strategies for information on how to help maintain compatibility of the app with future MATLAB releases. To create new apps interactively, Develop Apps Using App Designer instead.

This example shows how to examine and run a prebuilt GUIDE app. The app displays a surface plot, adds random noise to the surface, and refreshes the plot at regular intervals. The app contains two buttons: one that starts adding random noise to the plot, and another that stops adding noise. The slider below the plot allows the user to set the refresh period between 0.01 and 2 seconds.

Open and Run the Example

Open Script

Open and run the app. Move the slider to set the refresh interval between 0.01 and 2.0 seconds. Then click the Start Randomizing button to start adding random noise to the plotted function. Click the Stop Randomizing button to stop adding noise and refreshing the plot.

Examine the Code

In GUIDE, click the Editor button to view the code.
Near the top of the Editor window, use the Go To button to navigate to the functions discussed below.

`ex_guide_timergui_OpeningFcn`

The ex_guide_timergui_OpeningFcn function executes when the app opens and starts running. This command creates the timer object and stores it in the handles structure.

handles.timer = timer(...
    'ExecutionMode', 'fixedRate', ...       % Run timer repeatedly.
    'Period', 1, ...                        % Initial period is 1 sec.
    'TimerFcn', {@update_display,hObject}); % Specify callback function.

The callback function for the timer is update_display, which is defined as a local function.

`update_display`

The update_display function executes when the specified timer period elapses. The function gets the values in the ZData property of the Surface object and adds random noise to it. Then it updates the plot.

handles = guidata(hfigure);
Z = get(handles.surf,'ZData');
Z = Z + 0.1*randn(size(Z));
set(handles.surf,'ZData',Z);

`periodsldr_Callback`

The periodsldr_Callback function executes when the user moves the slider. It calculates the timer period by getting the slider value and truncating it. Then it updates the label below the slider and updates the period of the timer object.

% Read the slider value
period = get(handles.periodsldr,'Value');
% Truncate the value returned by the slider.
period = period - mod(period,.01);
% Set slider readout to show its value.
set(handles.slidervalue,'String',num2str(period))
% If timer is on, stop it, reset the period, and start it again.
if strcmp(get(handles.timer, 'Running'), 'on')
    stop(handles.timer);
    set(handles.timer,'Period',period)
    start(handles.timer)
else               % If timer is stopped, reset its period.
    set(handles.timer,'Period',period)
end

`startbtn_Callback`

The startbtn_Callback function calls the start method of the timer object if the timer is not already running.

if strcmp(get(handles.timer, 'Running'), 'off')
    start(handles.timer);
end

`stopbtn_Callback`

The stopbtn_Callback function calls the stop method of the timer object if the timer is currently running.

if strcmp(get(handles.timer, 'Running'), 'on')
    stop(handles.timer);
end

`figure1_CloseRequestFcn`

The figure1_CloseRequestFcn callback executes when the user closes the app. The function stops the timer object if it is running, deletes the timer object, and then deletes the figure window.

if strcmp(get(handles.timer, 'Running'), 'on')
    stop(handles.timer);
end
% Destroy timer
delete(handles.timer)
% Destroy figure
delete(hObject);