Basics of MATLAB and Beyond

handles into a vector when they are defined. That is, we want to modifythe code as follows:function exradio2(action)if nargin = = 0clfh1 = uicontrol(’Position’,[200 321 90 25], ...’String’,’JJJ’, ...’Style’,’radiobutton’,...’CallBack’,’exradio2(1)’);::h4 = uicontrol(’Position’,[200 246 90 25], ...’String’,’5AD’, ...’Style’,’radiobutton’,...’CallBack’,’exradio2(1)’);% Save radio button handles in h for later use.h = [h1 h2 h3h4];elseind = find(h~ = gco);set(h(ind),’value’,0);endThis implementation will not work because function variables are local tothe function and do not persist from one function call to another. Whena radio button is pushed it will issue a callback to exradio2, which willgo to the else section of code where it will crash because the variableh will not be defined. One way to implement the idea correctly is todeclare the vector h to be global. Global variables are visible to all otherfunctions that declare them global, and thus they will be visible betweenone function call and the next. The correct implementation will befunction exradio2(action)global hif nargin = = 0clf::You can even access such global variables from the matlab workspace(the command window) by declaring them global there.Variables in UserDataA problem with global variables is that they are vulnerable to beingcleared by the user from the workspace. If the user clears the globalvariables that a function expects to be present, then the function willc○ 2000 by CRC Press LLC