How to create a programme that will increase its increment of the size of array with a push button ? Using GUIDE

function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
x = (1:1);
a = get(handles.listbox1,'Value');
x(end+1)= a;
set(handles.text3,'String',num2str(a));
disp(x);

Basically, I want to create an array of variables with different values each and play them with function 'sound'. The array of variables are selected by user using variables from listbox and are added into array using 'add pushbutton'. For example I have a listbox of 'A' 'B' 'C', and when the user chose the order 'C' 'A' 'A' 'B' 'B' to be sounded. How do I create that code to put in what user selected from listbox and put them into array accordingly?

[Jan]

I do not undestand, what you are asking for.

What is the purpose of:

x = (1:1);

[Teo Say Yee]

@Jan Hi, I wanted to create a variable for the programme like this for example : Song = [ A A B B C ], then sound(Song,fs). Each of the A B C variables have their own values (harmonic frequency values which are double data type). So when user clicked 'add button' with their selection, it will be added to the variable 'song'. its like variables in variables. I am not sure if im making sense.

Answer 1

[Jan]

With some guessing:

function pushbutton1_Callback(hObject, eventdata, handles)
Value = get(handles.listbox1, 'Value');
Data  = get(handles.listbox1, 'String');
Selected = Data{Value};

% Append selection from list box to text field:
old = get(handles.text3, 'String');
set(handles.text3, 'String', [old, Selected]);
end

[Teo Say Yee]

hi @Jan, thanks for answering my question, your answer is close to what i want but what if i were to make the 'C' 'A' 'A' 'B' 'B' selected by user and put them into a variable ?

[Jan]

If this callback is called, if does put the the characters in a variable already, which is stored in handles.text3.String . You can access it from there in all other callbacks. There is no need to store the data twice.

[Teo Say Yee]

Also when i use get(handles.text3, 'string') as a variable into sound(), it says it must be real and floating point. How do i convert that ?

[Jan]

Yes, of course. See: doc sound

The sound() command needs a numerical signal, not a set of characters. 'A' is not a signal. You have to define the frequencies and the duration. Then sin() let you create a corresponding signal.

[Teo Say Yee]

Ah okay so i noticed A is a string in this case and i have an A variable(lets say ).

Is there a way to convert or connect a string to existing variable which both have the same name ?

[Jan]

It is not clear, what you are asking for. Maybe this helps:

S.A = '';
S.B = '';

Str = 'A';
S.(Str) = [S.(Str), Str]

[Teo Say Yee]

@Jan Thank you for replying me still. I will try to explain using some of my real programme to show you what im trying to do.

Basically, I want the user to create their own music and add the selected notes into a variable at 'Line 1' and to be played. I am struggling to create a programme for this coding part. I am able to set strings to 'Line 1' like what you have shown me, but i couldn't play those notes in 'Line 1' with sound function because strings are not variable as we know. So is there a way to connect strings and variables which both have the same name ? or is there other way to do the programme ?

[Jan]

"connect strings and variables which both have the same name" - this is far too complicated. Use the contents of the string to decide, which sound to play:

Str = '';
% Now append the notes in the callbacks - here emulated by code:
Str = [Str, 'C3 '];
Str = [Str, 'D3 '];
Str = [Str, 'C4 '];
... etc.

Finally you can "play" the notes:

Notes = strsplit(Str, ' ');  % ==> {'C3', 'D3', 'C4', ...}
for k = 1:numel(Notes)
   switch Notes{k}
       case 'C3'
           freq = 130.81;
           ...
   end
   sound(sin(freq * 2 * pi * (0:1/8192:.4)));
end
% See: https://pages.mtu.edu/~suits/notefreqs.html

See also:

• https://www.mathworks.com/matlabcentral/fileexchange/21262-matlab-piano
• https://www.mathworks.com/matlabcentral/fileexchange/28394-jaudio-buffered-sound-class
• https://www.mathworks.com/matlabcentral/fileexchange/74009-matlab-chords
• https://www.mathworks.com/matlabcentral/fileexchange/71836-piano