Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1996
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1996

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

Search the Archive

Re: multinomials: a programming question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg3948] Re: multinomials: a programming question
  • From: Count Dracula <lk3a at kelvin.seas.virginia.edu>
  • Date: Fri, 10 May 1996 03:32:54 -0400
  • Organization: University of Virginia
  • Sender: owner-wri-mathgroup at wolfram.com

In Message-ID: <4menll$jva at dragonfly.wolfram.com> Jack Goldberg 
<jackgold at admin.lsa.umich.edu> writes:

> I need to write the trinomial expansion 
> out in terms of Sum.  Something like this:

> tri[a_,b_,c_,n_] := Sum[Multinomial[i,j,k]*a^i*b^j*c*k, ???]
> where  i+j+k = n. 


In[3]:= <<DiscreteMath`Combinatorica`

f[{a_, b_, c_}, {i_, j_, k_}] := Multinomial[i, j, k] a^i b^j c k

tri[x_List, n_Integer] := Apply[Plus, (f[x, #1] & ) /@ Compositions[n, 3]]


In[5]:= tri[{a, b, c}, 3]

                            2                          2
Out[5]= 3 c + 6 a c + 3 a  c + 6 b c + 6 a b c + 3 b  c

In[6]:= tri[{1, 3, 5}, 4]

Out[6]= 2500
-- 
___________________________________________________________________________________
Levent Kitis           lk3a at cars.mech.virginia.edu    lk3a at kelvin.seas.virginia.edu
University of Virginia Department of Mechanical, Aerospace, and Nuclear Engineering  

==== [MESSAGE SEPARATOR] ====


  • Prev by Date: Re: Q: Documenting packages: TeX-style available
  • Next by Date: Inverse of IntegerDigits? and "Index" function?
  • Previous by thread: ShowGraph point size
  • Next by thread: multinomials: a programming question