conversion of sum of two sine wave from time domain to frequency domain

I am writing a code to convert the sum of two sine wave in matlab's appdesigner in which while plotting it is it is showing the plot when frequencies are changed but as soon as I change the value in amplitude slider from zero the graph is not being plotted. the complete code is below:

classdef app_5 < matlab.apps.AppBase
    
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure       matlab.ui.Figure
        PLOTButton     matlab.ui.control.Button
        a2Slider       matlab.ui.control.Slider
        a2SliderLabel  matlab.ui.control.Label
        a1Slider       matlab.ui.control.Slider
        a1SliderLabel  matlab.ui.control.Label
        f2Slider       matlab.ui.control.Slider
        f2SliderLabel  matlab.ui.control.Label
        f1Slider       matlab.ui.control.Slider
        f1SliderLabel  matlab.ui.control.Label
        UIAxes         matlab.ui.control.UIAxes
    end
    
    % Callbacks that handle component events
    methods (Access = private)
        
        % Value changed function: f1Slider
        function f1SliderValueChanged(app, event)
            value = app.f2Slider.Value;
            value = app.f1Slider.Value;
            fr1= app.f1Slider.Value;
            fr2= app.f2Slider.Value;
            am1= app.a1Slider.Value;
            am2= app.a2Slider.Value;
            fs=1000;
            t= 0:0.01:100*pi;
            w1=  2*pi*fr1;
            w2=  2*pi*fr2;
            y= am1*sin(w1*t);
            z= am2*sin(w2*t);
            x= y+z;
            number_of_samples=numel(t);
            f=0:fs/number_of_samples:fs-fs/number_of_samples;
            lx=numel(x);
            xn_fft=fft(x,lx);
            xf=abs(xn_fft);
            m=numel(f);
            for i=1:m
                plot(app.UIAxes,f(1:i),xf(1:i));
                drawnow;
            end
            
            
        end
        
        % Value changed function: f2Slider
        function f2SliderValueChanged(app, event)
            value = app.f2Slider.Value;
            value = app.f1Slider.Value;
            fr1= app.f1Slider.Value;
            fr2= app.f2Slider.Value;
            am1= app.a1Slider.Value;
            am2= app.a2Slider.Value;
            fs=1000;
            t= 0:0.01:100*pi;
            w1=  2*pi*fr1;
            w2=  2*pi*fr2;
            y= am1*sin(w1*t);
            z= am2*sin(w2*t);
            x= y+z;
            number_of_samples=numel(t);
            f=0:fs/number_of_samples:fs-fs/number_of_samples;
            lx=numel(x);
            xn_fft=fft(x,lx);
            xf=abs(xn_fft);
            m=numel(f);
            for i=1:m
                plot(app.UIAxes,f(1:i),xf(1:i));
                drawnow;
            end
            
            
        end
        
        % Value changed function: a1Slider
        function a1SliderValueChanged(app, event)
            value = app.f2Slider.Value;
            value = app.f1Slider.Value;
            fr1= app.f1Slider.Value;
            fr2= app.f2Slider.Value;
            am1= app.a1Slider.Value;
            am2= app.a2Slider.Value;
            fs=1000;
            t= 0:0.01:100*pi;
            w1=  2*pi*fr1;
            w2=  2*pi*fr2;
            y= am1*sin(w1*t);
            z= am2*sin(w2*t);
            x= y+z;
            number_of_samples=numel(t);
            f=0:fs/number_of_samples:fs-fs/number_of_samples;
            lx=numel(x);
            xn_fft=fft(x,lx);
            xf=abs(xn_fft);
            m=numel(f);
            for i=1:m
                plot(app.UIAxes,f(1:i),xf(1:i));
                drawnow;
            end
            
        end
        
        % Value changed function: a2Slider
        function a2SliderValueChanged(app, event)
            value = app.f2Slider.Value;
            value = app.f1Slider.Value;
            fr1= app.f1Slider.Value;
            fr2= app.f2Slider.Value;
            am1= app.a1Slider.Value;
            am2= app.a2Slider.Value;
            fs=1000;
            t= 0:0.01:100*pi;
            w1=  2*pi*fr1;
            w2=  2*pi*fr2;
            y= am1*sin(w1*t);
            z= am2*sin(w2*t);
            x= y+z;
            number_of_samples=numel(t);
            f=0:fs/number_of_samples:fs-fs/number_of_samples;
            lx=numel(x)
            xn_fft=fft(x,lx);
            xf=abs(xn_fft);
            m=numel(f);
            for i=1:m
                plot(app.UIAxes,f(1:i),xf(1:i));
                drawnow;
            end
            
        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 UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title')
            xlabel(app.UIAxes, 'X')
            ylabel(app.UIAxes, 'Y')
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.XLim = [0 10];
            app.UIAxes.YLim = [-10 10];
            app.UIAxes.XAxisLocation = 'origin';
            app.UIAxes.Position = [1 1 640 270];
            
            % Create f1SliderLabel
            app.f1SliderLabel = uilabel(app.UIFigure);
            app.f1SliderLabel.HorizontalAlignment = 'right';
            app.f1SliderLabel.Position = [12 444 25 22];
            app.f1SliderLabel.Text = 'f1';
            
            % Create f1Slider
            app.f1Slider = uislider(app.UIFigure);
            app.f1Slider.Limits = [0 10];
            app.f1Slider.ValueChangedFcn = createCallbackFcn(app, @f1SliderValueChanged, true);
            app.f1Slider.Position = [58 453 150 3];
            
            % Create f2SliderLabel
            app.f2SliderLabel = uilabel(app.UIFigure);
            app.f2SliderLabel.HorizontalAlignment = 'right';
            app.f2SliderLabel.Position = [385 444 25 22];
            app.f2SliderLabel.Text = 'f2';
            
            % Create f2Slider
            app.f2Slider = uislider(app.UIFigure);
            app.f2Slider.Limits = [0 10];
            app.f2Slider.ValueChangedFcn = createCallbackFcn(app, @f2SliderValueChanged, true);
            app.f2Slider.Position = [431 453 150 3];
            
            % Create a1SliderLabel
            app.a1SliderLabel = uilabel(app.UIFigure);
            app.a1SliderLabel.HorizontalAlignment = 'right';
            app.a1SliderLabel.Position = [18 363 25 22];
            app.a1SliderLabel.Text = 'a1';
            
            % Create a1Slider
            app.a1Slider = uislider(app.UIFigure);
            app.a1Slider.Limits = [0 10];
            app.a1Slider.ValueChangedFcn = createCallbackFcn(app, @a1SliderValueChanged, true);
            app.a1Slider.Position = [64 372 150 3];
            
            % Create a2SliderLabel
            app.a2SliderLabel = uilabel(app.UIFigure);
            app.a2SliderLabel.HorizontalAlignment = 'right';
            app.a2SliderLabel.Position = [384 363 25 22];
            app.a2SliderLabel.Text = 'a2';
            
            % Create a2Slider
            app.a2Slider = uislider(app.UIFigure);
            app.a2Slider.Limits = [0 10];
            app.a2Slider.ValueChangedFcn = createCallbackFcn(app, @a2SliderValueChanged, true);
            app.a2Slider.Position = [430 372 150 3];
            
            % Create PLOTButton
            app.PLOTButton = uibutton(app.UIFigure, 'push');
            app.PLOTButton.Position = [271 296 100 22];
            app.PLOTButton.Text = 'PLOT';
            
            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end
    
    % App creation and deletion
    methods (Access = public)
        
        % Construct app
        function app = app_5
            
            % Create UIFigure and components
            createComponents(app)
            
            % Register the app with App Designer
            registerApp(app, app.UIFigure)
            
            if nargout == 0
                clear app
            end
        end
        
        % Code that executes before app deletion
        function delete(app)
            
            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end

The image of the app is attached with the post.

Please help me how can I rectify the problem

[Walter Roberson]

            value = app.f2Slider.Value;
            value = app.f1Slider.Value;

Why are you reading both sliders, but storing the information into the same place, the second value overwriting the first? At best this is confusing to the readers; at worst it is a bug.

[Anupriya Bhardwaj]

thank you very much sir for telling me my mistake it is rectified

[Walter Roberson]

Note that you did that a number of times in your code.