Date: Aug 1, 1996 2:07 AM
Author: Dwarf
Subject: Piecewise Functions

I am trying to use Mma to solve a model where the system behaves a 
certain way up to a point, and an entirely different way after that
point. The result is something like:

f[x_/;x<4]:=0
f[x_/;x>=4]:=InterpolatingFunction<<...>>

This part I can get to work no problem. For part of my analysis, I would
like to take the derivative of the function, but all I get is an identity

In[5]
f'[x]

Out[5]
f'[x]

Can anyone help?

+----------------------------+
| | I understand mine's a risky plan,
| Greg Anderson | and your system can't miss
| dwarf@wam.umd.edu | but is security, after all a cause
| timbwolf@eng.umd.edu | or symptom of happiness.
| |
+----------------------------+ Dream Theater -- A Matter of Time