MATLAB GUI Radio Button variable storage - matlab

Question

I am an engineering student, fairly new to MATLAB. I have created a GUI for a class that calculates voltages and amperages of a specified circuit. I wish to display the amperages as (A) and (mA). The program currently calculates the data and displays it in static text boxes. I am using a button group with two radio buttons inside, working exclusively. I have used selectionChangeFcn in the following manner to control the buttons.
function group_SelectionChangeFcn(hObject, eventdata, handles)
switch get(eventdata.NewValue,'Tag') % Get Tag of selected object.
case 'radiobutton1'
var=1;
set(handles.text1, 'String', '(A)');
case 'radiobutton2'
var=1000;
set(handles.text1, 'String', '(mA)');
otherwise
end
Choosing one button or the other changes text in the static text boxes, and assigns a value to a variable. The bulk of the programming code is executed under a pushbutton. All of the variables are contained in this code, and are filled from edit boxes. Everything else works great so far. Within the cases I have (A) or (mA) outputted to a static text box, and you can see that operating the buttons does in fact display different values.
My problem is this; I wish to use variable var in the code to multiply my answer data so that it reads in either A or mA. Like this;
set (handles.text36,'string',num2str(ir1*var,'%20.3f'))
I cannot get this to work, however, the error says that var is undefined. It seems to do this in all circumstances. I have experimented with moving the code to different locations, but I cannot get it to work. Any help or ideas would be appreciated.

Answer 1

From what it looks like var is defined within the switch statement, thus it’s scope is just inside of the switch. You should define var outside of the switch to make its scope open to the function.
Also, when writing code in stack overflow, have a line break between your paragraph and indent the code 4 spaces and it’ll be formatted like a block of code, see below. Finally, include line breaks so one can determine easily where your lines of code are.
switch (...)
methods
end

Answer 2

You might profit from reading these articles:
http://www.mathworks.de/de/help/matlab/matlab_prog/base-and-function-workspaces.html
http://www.mathworks.de/de/help/matlab/creating_guis/ways-to-manage-data-in-a-guide-gui.html#f5-998711
You'll have to store var somewhere where it's accessible from other gui-functions.
One example:
Change & store var in your first function, e.g. as part of the handles structure:
% set var as a field on handles
handles.var = 1000;
% save the guidata - don't miss this!
guidata(hObject, handles);
In your second function, that's supposed to use var you can now take var from the handles structure:
set(handles.text36,'string',num2str(ir1*handles.var,'%20.3f'))

Answer 3

Based on the idea that your set line is not in the same function as the other methods, you must have the var either defined globally, sent through the function calls, or saved to handles or some other object. Here is a method of saving data that can be accessed from any function.
First, save the handle to the main gui, to the root address. Call this in the Main_OpeningFcn of your program.
setappdata(0, ‘mainGUI’, gcf);
Then, in your code call
mainGUI = getappdata(0, ‘mainGUI’);
var = someValue;
setappdata(mainGUI, ‘var’, var);
This saves the var variable inside of mainGUI. Now you have access to var from wherever you want just by calling getappdata. You do have to get mainGUI first, but that is only one line. Doug Hull has a video on MatLabCentral. I can find the link for you later that discusses this in more detail. One benefit with this method is that you don’t have to keep passing the handle structure around if you don’t need it.