MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

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


Hmmm, here there is everything ok.... :)


In[547]:=
L[k1_, k2_, alpha_, beta_ ] = Total[Log[
    q[k1, k2]]] + Total[(y - alpha - beta*q[k1, k2])^2/q[k1, k2]]


Out[547]=
\!\(1\/q[k1, k2] + q[k1, k2] + \((\(-alpha\) + y - beta\ q[k1,
k2])\)\^2\)

In[548]:=
D[L[k1,k2,alpha,beta],alpha]

Out[548]=
-2 (-alpha+y-beta q[k1,k2])
smanky at gmx.de napisal(a):
> 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.
>
> ∂\_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:
> http://www.mathematica-users.org/webMathematica/wiki/wiki.jsp?pageName=Special:Forum_ViewTopic&pid=10721#p10721
> Posted through http://www.mathematica-users.org [[postId=10721]]


  • Prev by Date: Re: Product and Summation sign
  • Next by Date: Re: Problem with a limit.
  • Previous by thread: Re: Beginner--getting rid of dot products with zero
  • Next by thread: RE:Beginner--getting rid of dot products with zero