Adding Drop Down Control

I am trying to add a Drop Down Control to my code that allows me to display only one signal (Sawtooth, Square, Triangle, Rectangle). I choose (Drop Down) from (Control) in the top bar. But I have no idea where to insert it in my code or how to make it work. Here is the code:

fs = 10000;

t = 0:1/fs:1.5;

x1 = sawtooth(2*pi*50*t);

x2 = square(2*pi*50*t);

subplot(2,1,1)

plot(t,x1)

axis([0 0.2 -1.2 1.2])

xlabel('Time (sec)')

ylabel('Amplitude')

title('Sawtooth Periodic Wave')

subplot(2,1,2)

plot(t,x2)

axis([0 0.2 -1.2 1.2])

xlabel('Time (sec)')

ylabel('Amplitude')

title('Square Periodic Wave')

Answer 1

[Cris LaPierre]

You can only add controls to a live script. Place it where you would define the waveform variable (here, x1 or x2). Assign the result to a variable. Its value will update based on what is selected. Use that variable in your plotting code.

Keep in mind that what is displayed in the dropdown can be different from what is executed (item value). Here's how I would do it.

Now toggle to selection, and the figure will display only the correspondingn waveform.

Answer 2

[Benjamin Kraus]

Write your code like this:

fs = 10000;
t = 0:1/fs:1.5;
wave = "Sawtooth";
f = str2func(lower(wave));
x = f(2*pi*50*t);
plot(t,x)
axis([0 0.2 -1.2 1.2])
xlabel('Time (sec)')
ylabel('Amplitude') 
title(wave + ' Periodic Wave')

Then highlight the word "Sawtooth" (including the quotation marks) and choose "Control" -> "Drop Down".

What you should see is this:

Now right-click on the drop-down and choose "Configure Control". You can add your additional strings there. "Item labels" is what users of the drop-down will see, and the "Item values" is the code that will be used. Make sure to include double-quotes in the "Item values".

Now when you pick a different item from the drop-down, your code will re-run with the chosen function.

Note: This will work for "Square" and "Sawtooth", but rectangle is a function in MATLAB that serves a different purpose (drawing rectangles in figures), so you would need to write your own implementation of that (and give it a different name, to avoid conflicting with the existing rectangle function), and triangle is also not a function, so you would need to write that.

[Benjamin Kraus]

Alternatively, a bit more advanced uses function handles instead of strings:

Write your code like this:

fs = 10000;
t = 0:1/fs:1.5;
f = @sawtooth;
x = f(2*pi*50*t);
plot(t,x)
axis([0 0.2 -1.2 1.2])
xlabel('Time (sec)')
ylabel('Amplitude') 
title([func2str(f) ' Periodic Wave'])

And when configuring the control, it should look like this:

(Converting the "s" to uppercase for the title is left as an exercise for the reader.)

[Benjamin Kraus]

I like @Cris LaPierre's solution better.