How to assign a user input to a variable in matlab when using uicontrol 'string'?

uicontrol('Parent',d,...
               'Style','edit',...
               'Position',[20 330 210 60],...
               'String','-4')

The -4 is just an example value, and can be changed by the user. I want to store this string value in a variable. Please help.

Thank you in advance.

Answer 1

[Stephen23]

hnd = uicontrol('Parent',d,... 'Style','edit',... 'Position',[20 330 210 60],... 'String','-4');
str = get(hnd,'String')
num = str2double(str)

[oshawcole]

I ran this command, the value of num come to be -4. If i dont specify the string, num= NaN. I want the string to be manipulated according to the user input. It should not always give me -4. For example if the user wants to give -7 as input, so num= -7. Thank you for the help.

[Stephen23]

"It should not always give me -4"

It does not always give you -4. It gives you whatever the string in the edit box is. Have a look at str.

"For example if the user wants to give -7 as input, so num= -7"

It works for me, did you try it?

>> hnd = uicontrol('Style','edit'); % then I added '-7' by hand
>> get(hnd,'String')
ans = -7
>>

What do you expect to happen?

Note that by default MATLAB uicontrols do not trigger any action, so the simplest way of updating a variable based on any uicontrol value (e.g. the string) is to get that value just as I showed you in my answer. If you want the uicontrol to trigger some callback then you will have specify one of its callback methods:

https://www.mathworks.com/help/matlab/ref/uicontrol-properties.html

or add some listener to your gui:

https://www.mathworks.com/help/matlab/matlab_oop/learning-to-use-events-and-listeners.html

[oshawcole]

heading = uicontrol('Parent',d,...
             'Style','text',...
             'Position',[20 310 210 100],...
             'String','Enter the first value:');
          txt = uicontrol('Parent',d,...
             'Style','edit',...
             'Position',[20 330 210 60],...
             'String',' -4');

This -4 is just an example value, like default answer in the dialog box. I want to extract the user input value and assign it to a variable. The user can use any number, as it is a user interactive code.

[Stephen23]

"I want to extract the user input value and assign it to a variable. The user can use any number, as it is a user interactive code."

That is exactly what my code does. What you think this example shows?:

>> hnd = uicontrol('Style','edit'); % then I added '+3' by hand
>> get(hnd,'String')
ans = +3

Call get any time you want to check what the current string is. It is that simple. If you want a callback then add a callback (in which case you will also need get or the new dot syntax, whichever works for you).

Are you expecting MATLAB to magically update a variable any time the user changes the string in the edit box? This is possible, but it is quite a bit fiddlier than what I showed you in my answer, and it would be worth considering using nested functions. Have a look at my FEX submission iregexp for an example of how to do this:

https://www.mathworks.com/matlabcentral/fileexchange/48930-interactive-regular-expression-tool