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MathGroup Archive 2006

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Re: Beginner--getting rid of dot products with zero

  • To: mathgroup at
  • Subject: [mg66851] Re: Beginner--getting rid of dot products with zero
  • From: "ben" <benjamin.friedrich at>
  • Date: Thu, 1 Jun 2006 06:55:30 -0400 (EDT)
  • References: <e5jsas$e48$>
  • Sender: owner-wri-mathgroup at

Hi Smanky,

I only understood half of your question,
maybe you could provide more information.

Why do you apply Total[]?
Are there vector quantities?

Usually, partial derivatives should be straigt-forward




smanky at schrieb:

> hello,
> i am economics student... not very familiar with mathematica yet.
> i am currently using mathematica to verify derivatives i need in another system's code. and, i am stuck with a not so uncommon problem. however, browsing forums i haven't found the solution for my particular version of the problem yet.
> when taking partial derivatives of this expression:
> L[k1_, k2_, alpha_, beta_ ] = Total[Log[q[k1, k2]]] + Total[(y - alpha - beta*q[k1, k2])^2/q[k1, k2]];
> e.g.
> &#8706;\_alpha\ L[k1, \ k2, \ alpha, \ beta]
> the results include terms like e.g.
> x.{0,0,0} or 0.{, ,}
> how can i get rid of those? one way is probably by using a replace rule, but this seems rather cumbersome, beside the mere fact that i didn't even get this to work, yet. Simplify, or FullSimplify don't help either.
> any suggestions are greatly appreciated.
> cheers,
> ~stephan
> Link to the forum page for this post:
> Posted through [[postId=10721]]

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