Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2001
*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 2001

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

Search the Archive

A=B example

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32120] A=B example
  • From: Erich Neuwirth <erich.neuwirth at univie.ac.at>
  • Date: Fri, 28 Dec 2001 02:41:35 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

this has probably been asked before.
being new to the list i would be happy with a pointer to previous
answers.


in A=B by Wilf and Zeilberger,
on page 61 there is the following program for deriving recursions
explicitly
(i had to change FactorialSimplify to FullSimplify
because the original version was for mathematica 2.2):


findrecur[f_, ii_, jj_] :=
  Module[{yy, zz, ll, tt, uu, r, s, i, j},
    yy = Sum[
        Sum[a[i, j] *FullSimplify[f[n - j, k - i]/f[n, k]], {i, 0, ii}],
{j, 
          0, jj}];
    zz = Collect[Numerator[Together[yy]], k];
    ll = CoefficientList[zz, k];
    tt = Flatten[Table[a[i, j], {i, 0, ii}, {j, 0, jj}]];
    uu = Flatten[Simplify[Solve[ll == 0, tt]]];
    For[r = 0, r <= ii, r++,
      For[s = 0, s <= jj, s++,
        a[r, s] = Replace[a[r, s], uu]]];
    Sum[Sum[a[i, j]  F[n - j, k - i], {i, 0, ii}], {j, 0, jj}] == 0]

defining
f[n_, k_] := n!/(n - k)!

and executing
findrecur[f,1,1]
works,
but trying to run exactly the same statement a second time
produces a lot of errors and effectively hangs mathematica.

is there a solution?



--
Erich Neuwirth, Computer Supported Didactics Working Group
Visit our SunSITE at http://sunsite.univie.ac.at
Phone: +43-1-4277-38624 Fax: +43-1-4277-9386


  • Prev by Date: Re: size of graphics for animation
  • Next by Date: Non-linear Boundary Diff equations
  • Previous by thread: RE: ParamtricPlot3D
  • Next by thread: Re: A=B example