Numeric Slider not changing in live editor

I'm new to the live editor. I want to add a loop with slider bar variables. And as the slider bar changes, the plot will change. But if there is no change, I still want other things in the plot to update. Here's some sample code that replicates what I'm seeing:

while true
    test1=7;
    fprintf('%i',test1)
    pause(1)
end

Except, where "test1=7" is, that is supposed to be a live editor numeric slider. But as I move that slider around, nothing happens. It just keeps printing "7" over and over. The slider controls are set to Run On "Value changing." And Run "Current section". The only thing that works is Run "All sections". But in my larger program, that is not what I want to do. It would take a long time to re-run everything just for one small variable change.

Is there anything I can do to make this work?

Thanks.

[Stephen23]

Why do you need the WHILE loop? The whole premise of LIveScripts is that they (can) re-run your code when something changes... so it looks as if you are trying to replicate the basic LiveScript functionality using a WHILE loop.

[Jon Kraft]

Thanks for your help. The reason for this is the plot is actually measuring real time sensor data. So even when I don't want to change a variable, I still want the plot to update. It sounds like you are saying this is not possible with a Live Script?

[Jon Kraft]

I've attached the test script, if that is helpful to see.

[Stephen23]

"The reason for this is the plot is actually measuring real time sensor data."

Please show the code you use to import the sensor data with.

[Jon Kraft]

Thanks again for your. Though I am surprised it is this difficult to do it in Live Script -- maybe I've made a basic mistake somewhere in my setup? The code for the sensor data is complex, but it is basically:

while true
    data = measureSensorData();
    test1=7;
    fprintf('%i',test1)
    plot(t, data);
    pause(1)
end

Answer 1

[Zuber Khan]

Hi,

I understand that you want to update the variable "test1" using an interactive slider and also want to update the plot irrespective of whether the slider variable has changed or not.

In MATLAB's live editor, when using a "while true" loop, the code inside the loop will keep executing without interruption, and it won't be responsive to changes in the user interface, such as moving a slider. If you remove the while loop, the variable "test1" will update according to the slider.

However, since you have explicitly specified that you need to use "while" loop to selectively update the plot irrespective of the change in the value of slider variable, there is a possible workaround to use a "while" loop that checks for updates to the slider value at each iteration and updates the plot accordingly. Although, this approach requires manual coding of the slider functionality instead of using the built-in Live Editor slider, it will help to achieve the desired behaviour.

% Create a figure and a slider control
fig = uifigure;
sld = uislider(fig, 'Position', [100, 75, 120, 3]);

% Initialize variables
test1 = sld.Value; % Initialize test1 with the slider's value
data = measureSensorData(); % Initial call to get data

% Create a plot
hPlot = plot(data);
xlim([1, length(data)]); % Set the x-axis limits

% Set up the update loop
while true
    % Check if the slider value has changed
    if sld.Value ~= test1
        test1 = sld.Value; % Update test1 with the new slider value
        % Perform any updates that depend on test1        
    end
    
    % Measure new sensor data
    data = measureSensorData();
    
    % Update the plot
    hPlot.YData = data;
    
    % Update the figure window
    drawnow;
    
    % Pause for a short period to prevent overwhelming the CPU
    pause(0.1);
end

function data = measureSensorData()
    data = rand(1,10);
end

Note that in the above code, I have defined "measureSensorData()" function randomly since it is not specified. You can update it accordingly to make it dependent on "test1" value as per your requirements.

I am also attaching the output of the code snippet as follows:

You can notice in the command window that altering the slider adjusts the "test1" variable's value accordingly, and the plot is updated regardless of any changes to the "test1" slider variable.

In case, you want the plot to change with the slider variable interactively, you can refer to the following documentation link:

https://in.mathworks.com/help/control/ug/build-app-with-interactive-plot-updates.html

To know more about creating the slider manually using the "uislider" function, kindly refer to the following documentation link:

https://in.mathworks.com/help/matlab/ref/uislider.html

I hope it resolves your query!

Best Regards

Zuber