[ff3d-users] about derivatives...

[sellier]

Hello everybody,

i am trying to write a code in ff3d to solve numerically a model but i have a
problem :) I have defined a function with the command "function" but if i do
something like

 d = dx(r);

the compiler says me something like

 cannot compute the derivative of a non FEM function

So, how can i do this? Is it possible to convert a non FEM function to a FEM
function? Can somebody help me? Thank a lot to anybody will help me! :)

Bien Amicalement

Jean Michel