Problem with the application GUIDE

Hi, i'm trying to plot a graph with implicits equations, this is my code :

function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
a = str2num(get(handles.textbox1,'String'));

fh = @(S,M) (M-(1/a)*(a-S)+S);
gh = @(S,M) (M-S)*(a*(M-S)*((1-a)*((a*S)/(a+S))+((a*a)/(a+S).^2)*(a-S))-(a-S).^2*((a*a)/(a+S).^2));

hold on
w=ezplot(fh,[0,10,0,10])
x=ezplot(gh,[0,10,0,10])

and MATLAB answers me

 Contour with properties:

    LineColor: 'flat'
    LineStyle: '-'
    LineWidth: 0.5000
         Fill: 'off'
    LevelList: 0
        XData: [1x251 double]
        YData: [251x1 double]
        ZData: [251x251 double]

Show all properties

Warning: Function failed to evaluate on array inputs; vectorizing the function may speed up its evaluation and avoid the
need to loop over array elements. 
> In ezplotfeval (line 56)
  In ezplot>ezimplicit (line 257)
  In ezplot (line 153)
  In aqwzsx>pushbutton1_Callback (line 111)
  In gui_mainfcn (line 95)
  In aqwzsx (line 42)
  In @(hObject,eventdata)aqwzsx('pushbutton1_Callback',hObject,eventdata,guidata(hObject)) 

x = 

    Contour with properties:

      LineColor: 'flat'
      LineStyle: '-'
      LineWidth: 0.5000
           Fill: 'off'
      LevelList: 0
          XData: [1x251 double]
          YData: [251x1 double]
          ZData: [251x251 double]

    Show all properties

So i don't know how to solve this problem...

Moreover i would like how to plot this two graphes with differents colors someone knows how to do it ?

Thanks a lot !!!!

Answer 1

[Walter Roberson]

ezplot() passes in equal-length column vectors for the two arguments to the function. Your code is expecting scalar values. ezplot() will notice the problem and will fall back to working with scalars, but it gives a warning when it does so. It is not an error message, it is a warning that you could be more efficient.

In particular, rewrite as

gh = @(S,M) (M-S).*(a*(M-S).*((1-a)*((a*S)./(a+S))+((a*a)./(a+S).^2).*(a-S)) - (a-S).^2.*((a*a)./(a+S).^2));

[Walter Roberson]

To change the colors, use

set(w, 'LineColor', 'r');   %red
set(x, 'LineColor', [.2, .9, .3])   %random RGB triple