Plot graph in App Designer

I need to plot a graph with the 2 axes being gain and frequency. The code is as below but I can't plot it since my gain is not numeric. How else should I plot it?

        % Button pushed function: LOWPASSFILTERButton
        function LOWPASSFILTERButtonPushed(app, event)
            % INPUT USED
            % R = Resistance (Ohms)
            % f = Frequency (Hz)
            % C = Capacitance (C)
            
            % OUTPUT
            % H(s) = Gain

            % To check selection for resistance
            selection = app.ResistanceOhmsDropDown.Value;

            % To assign a value to the selections
            if selection == '1k'
                value = 1;
            elseif selection == '2k'
                value = 2;
            elseif selection == '3k'
                value = 3;
            elseif selection == '4k'
                value = 4;
            end

            % Conditions for each selections
            switch value
                case 1
                    % specify inputs
                    R = 1000;
                    f = app.CutoffFrequencyHzEditField.Value;
                    C = 1/(2*pi*R*f);

                    % Calculate gain
                    gain = tf(1,1+(2*pi*R*C));

                    % plot graph
                    plot(app.UIAxes,gain,f);
            end

Answer 1

[Walter Roberson]

Change

                    plot(app.UIAxes,gain,f);

to

                   bodeplot(app.UIAxes, gain, {0,f} );

[Ye Ken Kok]

It displays an error

[Walter Roberson]

That is a nuisance. You will need to do something like

[mag, phase, w] = bode(gain, {1, f});

That will return the magnitude and phase responses, and the frequencies corresponding. Normally magnitude and phase would be in separate plots, but you can proceed to plot(app.UIAxes, w, mag) and do whatever is suitable for the phase.

[Ye Ken Kok]

Well I tried what you said, but it showed another error stating that the data should not have 2 dimensions

[Walter Roberson]

%setup for demo purposes
app.UIFigure = figure(); %uifigure();
app.UIFigure.Position = [100 100 1222 499];
app.UIAxes = uiaxes(app.UIFigure);
f = 50;
%end setup for demo


R = 1000;
C = 1/(2*pi*R*f);
gain = tf(1, 1+(2*pi*R*C))

gain =
 
  0.9804
 
Static gain.

[mag, phase, w] = bode(gain, {1, f});
plot(app.UIAxes, w, squeeze(mag), 'DisplayName', 'magnitude')
hold(app.UIAxes, 'on');
plot(app.UIAxes, w, squeeze(phase), 'DisplayName', 'phase');

legend show

[Ye Ken Kok]

After I run the program the graph is plotted on the GUI but the legend appears in another tab

[Walter Roberson]

legend(app.UIAxes, 'show')

Note: you are never going to have negative frequencies for this purpose.