Make an iucontrol edit box into a number able to be done math on.

"lat" should be a double and should be able to be subtracted from 90. How do I make "lat" a double and able to be done math on?

lat = uicontrol('Style','edit','String','0','position',[250 630 100 20],'Callback',(@h_lat));
  uicontrol('Style','pushbutton','String','Evaluate','Position',[130,550,100,50],'Callback',{@Evaluate},'BackgroundColor','green');
  function h_lat(hObject, eventdata, handles)%#ok
      lat = str2double(get(hObject,'String'));
      handles = guidata(hObject);
      guidata(hObject, setfield(handles,'lat',lat));%#ok

    function Evaluate(hObject, eventdata, handles)
        handles = guidata(hObject);
        lat = handles.lat;
        disp(lat);
        Theta=(90-lat)*pi/180;

Output:

UIControl (0) with properties:

                Style: 'edit'
               String: '0'
      BackgroundColor: [0.9400 0.9400 0.9400]
             Callback: @h_lat
                Value: 0
             Position: [250 630 100 20]
                Units: 'pixels'

    Show all properties

Undefined function 'minus' for input arguments of type 'matlab.ui.control.UIControl'.

Error in MagneticFieldFromLonLat>Evaluate (line 64)
    Theta=(90-lat)*pi/180;

Error while evaluating UIControl Callback

[Adam]

Why are you naming both the uicontrol and the converted string you get out of that with the same name 'lat'? That is almost certainly the root of your problem.

handles.lat is apparently the uicontrol when you come to use it.

[Philosophaie]

Normally this given as "lat" as a double and you can do math on it. Why is it not in this case?

[Adam]

lat = uicontrol('Style','edit','String...

Name that something else for a start.