[PD] help with expr and differential equation

[ronni montoya]

Hi, im trying to implement the lokta volterra equation using expr in pd :

http://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equation



im doing in this way:

 [expr $f1 * ($f3 - ($f4 * $f2));
          $f2 * ($f5 - ($f6 * $f1)); ]



but im not the getting the expected result, im only getting the output
of the second outlet but  with wierd results, any idea what am i doing
wrong?



thanks



R.