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Topic: Piecewise Functions
Replies: 1   Last Post: Aug 7, 1996 3:56 AM

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George Jefferson

Posts: 12
Registered: 12/7/04
Re: Piecewise Functions
Posted: Aug 7, 1996 3:56 AM
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: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

oddly, I just ran into the same need.
of course,

D[f[x],x]

not knowing which piece of f to apply..can only return:

f'[x]

but

D[f[x],x] /. x-> 0

gives

f'[0]

where it seems it could just return 0..

i'm stumped..







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