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symbolic differentiation of a scalar field

• To: mathgroup at smc.vnet.net
• Subject: [mg103349] symbolic differentiation of a scalar field
• From: Llewlyn <tommaso.biancalani at gmail.com>
• Date: Wed, 16 Sep 2009 05:48:56 -0400 (EDT)

Greetings,

I have a function depending by n (large) number of variables, that is f
(x1 .. xn).
I need to do to some symbolic calculus with this function, basically
differentiation.
Supposing n=10 here's my solution:

f[ Array[a_, 10] ] := Sum [i*a[i], {i,10}]
dfdk[ k_ ] := D[ f[Array[a_, 10]], a[k]]

How do you think of? And how may i do for an unknown n, set of
variables?
I've tried searching tutorial for standard techinque but i didn't find
one, links are really welcome.

bests,

Ll.

• Follow-Ups:
  • Re: symbolic differentiation of a scalar field
    • From: Leonid Shifrin <lshifr@gmail.com>