Getting my listbox to connect with a graph

Hello,

I am new to MATLAB but I am creating a GUI for a project.

What I am trying to do with the GUI is have a list box with three different functions to select. Once a function is clicked, it will be plotted in the graph.

below is the callback but I have the three functions set up to be plotted, I'm just struggling on the technical aspects.

% --- Executes on selection change in listbox1.
function listbox1_Callback(hObject, eventdata, handles)
% hObject    handle to listbox1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% squared function
 % squared function

X=0:0.1:3
Y=2.^X
plot(X,Y), grid on

%graph ln(x)
x= [0 1 2 3 4 5 6 7 8 9]
y=log(x)
plot(x,y), grid on 

%cos
t = -pi:0.01:3*pi; 
plot(t,cos(t)), grid on

% Hints: contents = cellstr(get(hObject,'String')) returns listbox1 contents as cell array
%        contents{get(hObject,'Value')} returns selected item from listbox1