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Matlab GUI - Using “msgbox” to Create a Better GUI 

18 Feb 2008 Quan Quach 20 comments 5,346 views

Introduction

 The msgbox command in Matlab can provide valuable informationto the user of your GUI. It can warn the user, inform the user of an

error, and also provide help. In this example, we will use a GUI

(shown below) consisting of a simple edit text component.

 The GUI takes in inputs between 0 to 100.

• If the user tries to input a numerical value that is not within 0-100,

then the GUI will spit out an error message.

• If you user tries to set the value to 100, the user will give off a

warning message.

• If you try to input something that is not a number, the user will get a

help message.

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The Example

1. First, download the GUI skeleton here. Unzip the files and place them

wherever you please.

2. Now, type guide at the command prompt.

3. Choose to open the sample GUI by clicking on “Open Existing GUI”.

Click on “Browse” to locate where you saved the GUI files.

4. Here is what the GUI should look like when you open it:

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5. Click on the icon on the GUI figure to bring up the

accompanying .m file.

6. Now, we want to add the following code to edit1_Callback.

7. input = get(handles.edit1,'String'); %get the input from the edit text

field

8. input = str2num(input); %change from string to number

9.

10.if isempty(input) %if the input is not a number

11.

12. %this is the first line of the msgbox

13. msgboxText{1} = 'You have tried to input something that is NOT

a number.';

14. %this is the second line

15. msgboxText{2} = 'Try an input between 0 and 100 instead.';

16.

17. %notice that msgboxText is a Cell array!

18.

19. %this command creates the actual message box

20. msgbox(msgboxText,'Input not a number', 'help');

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21.

22.elseif input == 100 %if the input is exactly 100

23. msgboxText{1} = 'You have chosen the highest possible input!';

24. msgboxText{2} = 'You cannot go any higher than this or it willresult in an error.';

25. msgbox(msgboxText,'Maximum input chosen', 'warn');

26.

27.elseif input < 0 || input > 100 %if the input is less than 0 or greater

than 100

28. msgboxText{1} = 'You have chosen a value outside the range of 

0-100!';

29. msgbox(msgboxText,'Input not allowed', 'error');

end

30.And that’s it! Run the GUI to make sure that it does what you expect

it too.

Other tips

 The msgbox command can be replaced with the errordlg, warndlg, and

helpdlg commands. It’s purely a matter of preference. For example:

msgbox('hello world', 'hello world','error');

 

%an equivalent command

errordlg('hello world','hello world')

Download the Source Files