Need help in dropdownopening callback.

I am designing an app for various signal display. (Attached UI and code).

1: Select a signal from dropdown. (how to write the callback for this)

2: Primary graph of that signal will be plotted on the axes. (how to write the callback for this)

3: Control the value of x axis and y axis from the slider. (how to write the callback for this)

classdef app1 < matlab.apps.AppBase

    % Properties that corr

    % Callbacks that handle component events
    methods (Access = private)

        % Value changed function: DropDown
        function DropDownValueChanged(app, event)
            x = 0:0.01: (360/180)*pi;
            y = sin(x);
             plot(app.UIAxes,y);
         
        end

        % Value changing function: Slider
        function SliderValueChanging(app, event)
         
        end

        % Drop down opening function: DropDown
        function DropDownOpening(app, event)

        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';

            % Create Panel
            app.Panel = uipanel(app.UIFigure);
            app.Panel.Title = 'Panel';
            app.Panel.Scrollable = 'on';
            app.Panel.Position = [171 43 400 342];

            % Create UIAxes
            app.UIAxes = uiaxes(app.Panel);
            title(app.UIAxes, 'sine signal')
            xlabel(app.UIAxes, 'x')
            ylabel(app.UIAxes, 'y')
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.XLim = [0 50];
            app.UIAxes.YLim = [0 50];
            app.UIAxes.XTick = [0 10 20 30 40 50];
            app.UIAxes.XTickLabel = {'0'; '10'; '20'; '30'; '40'; '50'};
            app.UIAxes.YTick = [0 25 50];
            app.UIAxes.YTickLabel = {'0'; '25'; '50'};
            app.UIAxes.XGrid = 'on';
            app.UIAxes.YGrid = 'on';
            app.UIAxes.Position = [42 14 325 100];

            % Create SliderLabel
            app.SliderLabel = uilabel(app.Panel);
            app.SliderLabel.HorizontalAlignment = 'right';
            app.SliderLabel.Position = [104 226 36 22];
            app.SliderLabel.Text = 'Slider';

            % Create Slider
            app.Slider = uislider(app.Panel);
            app.Slider.ValueChangingFcn = createCallbackFcn(app, @SliderValueChanging, true);
            app.Slider.Position = [161 235 186 7];

            % Create Slider2Label
            app.Slider2Label = uilabel(app.Panel);
            app.Slider2Label.HorizontalAlignment = 'right';
            app.Slider2Label.Position = [104 156 42 22];
            app.Slider2Label.Text = 'Slider2';

            % Create Slider2
            app.Slider2 = uislider(app.Panel);
            app.Slider2.Position = [167 165 180 7];

            % Create xLabel
            app.xLabel = uilabel(app.Panel);
            app.xLabel.Position = [41 215 52 33];
            app.xLabel.Text = 'x';

            % Create yLabel
            app.yLabel = uilabel(app.Panel);
            app.yLabel.Position = [41 148 44 39];
            app.yLabel.Text = 'y';

            % Create DropDownLabel
            app.DropDownLabel = uilabel(app.Panel);
            app.DropDownLabel.HorizontalAlignment = 'right';
            app.DropDownLabel.Position = [41 281 65 22];
            app.DropDownLabel.Text = 'Drop Down';

            % Create DropDown
            app.DropDown = uidropdown(app.Panel);
            app.DropDown.Items = {'Sine signal', ''};
            app.DropDown.ItemsData = {'y=sin(x)'};
            app.DropDown.DropDownOpeningFcn = createCallbackFcn(app, @DropDownOpening, true);
            app.DropDown.ValueChangedFcn = createCallbackFcn(app, @DropDownValueChanged, true);
            app.DropDown.Position = [121 269 237 46];
            app.DropDown.Value = 'y=sin(x)';

            

Answer 1

[Srijith Kasaragod]

Assuming the x and y sliders adjust x-axis limit and y-axis limit of the plot respectively, following lines of code shows one of the possible solution to the problem.

The app contains dropdown, x-slider, y-slider, axes and a button. Dropdown enables selection of signals, i.e, either sin or cos. The x-slider and y-slider adjusts the x-axis limit and y-axis limit of the axes. Clicking on the push-button generates signal plot with axes limits as specified.

App variables required to hold user input are:

properties (Access = private)
    func; % variable to hold the signal selected from dropdown
    xslider; % variable to hold upper limit of xlim
    yslider; % variable to hold upper limit of ylim
end 

Startup function callback saves default values of dropdown and sliders into app variables.

function startupFcn(app)
    app.func= str2func(app.SignalDropDown.Value); %str2func creates function handle from string
    app.xslider= app.XSlider.Value;
    app.yslider= app.YSlider.Value;
    
end

Signal dropdown callback function saves the user selected signal into app variable 'func'.

function SignalDropDownValueChanged(app, event)
    value = app.SignalDropDown.Value;
    app.func= str2func(value); 
end

Pushbutton callback function holds the x, y values, generates the plot and sets xlim and ylim as per user input.

function EnterButtonPushed(app, event)
    x=0:0.01:(360/180)*pi;
    y= app.func(x);
    plot(app.UIAxes,x,y);
    xlim(app.UIAxes,[0 app.xslider]);
    ylim(app.UIAxes,[-2 app.yslider]);
end

Slider callback functions saves user input into app variables 'xslider' and 'yslider'.

function XSliderValueChanged(app, event)
    app.xslider = app.XSlider.Value;
end

function YSliderValueChanged(app, event)
    app.yslider = app.YSlider.Value;
end

All components can be placed in the app as per user requirement. Refer this link to read more about 'str2func' function.