Two plots on same axes using guide

Hello!

I have two global variables y & z that I am wanting to plot against the same x-axis. The GUI has two check boxes one to plot y and the other to plot z. I want to be able to show both plots at the same time so that I can compare the two. But I am also wanting them to show if and only if I check the box assigned to the global variable.

right now the code shows one plot if I click checkbox1, but that plot disappears when I click checkbox2 and only checkbox2 plot would show. I tried to use hold on, as well as hold(handles.axes1,'on') but that didn't work.

here is the code:

    function checkbox1_Callback(hObject, eventdata, handles)

    gatherAndUpdate(handles)

    function gatherAndUpdate(handles)

    gatheredData = gatherData(handles);

    updateAxes(handles.axes1,gatheredData);

    function gatheredData = gatherData(handles)

    gatheredData.PlotData = get(handles.checkbox1,'value');

    function updateAxes(axesToUse,gatheredData)

    handles.axes1=(axesToUse)

    if gatheredData.PlotData

    x=linspace(5,20,120000);

    global y

    axes(handles.axes1)

    plot(x,y);

    else

    x=linspace(5,20,120000);
    set(plot(x,y),'visible','off') 
    end

    function checkbox2_Callback(hObject, eventdata, handles)

    gatherAndUpdate2(handles)

    function gatherAndUpdate2(handles)

    gatheredData2 = gatherData2(handles);

    updateAxes2(handles.axes1,gatheredData2);

    function gatheredData2 = gatherData2(handles)

    gatheredData2.PlotData = get(handles.checkbox2,'value');

    function updateAxes2(axesToUse,gatheredData2)

    handles.axes1=(axesToUse)

    if gatheredData2.PlotData

    x=linspace(5,20,120000);

    global z

    axes(handles.axes1)

    plot(x,z);

    else x=linspace(5,20,120000);

    set(plot(x,z),'visible','off')
    end
      end