D and Derivative - help please
- To: mathgroup at yoda.ncsa.uiuc.edu
- Subject: D and Derivative - help please
- From: uunet!uthvm1.bitnet!AN123651
- Date: Thu, 22 Mar 90 12:41:28 CST
I would appreciate some help with this from anyone who understands
Mathematica better than I. Suppose I define a function:
f[x_,y_] := x + y + Gamma[x,y]
When I take its derivative using D, everything is fine.
D[f[x,y],x]
(1,0)
1 + Gamma [x, y]
Derivative, on the other hand, can't get as far.
Derivative[1,0][f]
(1,0)
f
Now, suppose I define my own value for the derivative of the
Gamma function.
Derivative[1,0][Gamma] = Plus
D understands this perfectly, but Derivative not at all.
D[f[x,y],x]
1 + x + y
Derivative[1,0][f]
(1,0)
f
Derivative[1,0][f][x,y]
(1,0)
f [x, y]
What's the difference here? How can I get Derivative to use my
definition?
Thanks for any help.
E. Neely Atkinson
AN123651 at UTHVM1.BITNET
neely at mdaali.cancer.utexas.edu