Opened 12 years ago
Last modified 4 years ago
#1291 new enhancement
solving recurrences
Reported by: | was | Owned by: | was |
---|---|---|---|
Priority: | major | Milestone: | sage-feature |
Component: | calculus | Keywords: | |
Cc: | burcin, kevin.stueve, kcrisman, robert.marik, eviatarbach, rws, ktkohl | Merged in: | |
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
This ticket would provide an interface to Maxima's and Sympy's recurrence-solving functions.
Maxima example:
sage: maxima.load('solve_rec') ?\/Users\/was\/s\/local\/share\/maxima\/5\.13\.0\/share\/contrib\/solve_rec\/solve_rec\.mac sage: print maxima('solve_rec(a[n]=a[n-1]+a[n-2]+n/2^n, a[n])') n n n (sqrt(5) - 1) %k (- 1) (sqrt(5) + 1) %k 1 n 2 2 a = ------------------------- - ---- + ------------------ - ---- n n n n n 2 5 2 2 5 2
Sympy example:
>>> from sympy import Function, rsolve >>> from sympy.abc import n >>> y = Function('y') >>> f = (n - 1)*y(n + 2) - (n**2 + 3*n - 2)*y(n + 1) + 2*n*(n + 1)*y(n) >>> rsolve(f, y(n)) 2**n*C0 + C1*factorial(n) >>> rsolve(f, y(n), { y(0):0, y(1):3 }) 3*2**n - 3*factorial(n)
The Maxima help:
sage: maxima.solve_rec? Maxima 5.13.0 http://maxima.sourceforge.net Using Lisp CLISP 2.41 (2006-10-13) Distributed under the GNU Public License. See the file COPYING. Dedicated to the memory of William Schelter. This is a development version of Maxima. The function bug_report() provides bug reporting information. (%i1) -- Function: solve_rec (<eqn>, <var>, [<init>]) Solves for hypergeometrical solutions to linear recurrence <eqn> with polynomials coefficient in variable <var>. Optional arguments <init> are initial conditions. `solve_rec' can solve linear recurrences with constant coefficients, finds hypergeometrical solutions to homogeneous linear recurrences with polynomial coefficients, rational solutions to linear recurrences with polynomial coefficients and can solve Ricatti type recurrences. Note that the running time of the algorithm used to find hypergeometrical solutions is exponential in the degree of the leading and trailing coefficient. To use this function first load the `solve_rec' package with `load(solve_rec);'. Example of linear recurrence with constant coefficients: (%i2) solve_rec(a[n]=a[n-1]+a[n-2]+n/2^n, a[n]); n n (sqrt(5) - 1) %k (- 1) 1 n (%o2) a = ------------------------- - ---- n n n 2 5 2 n (sqrt(5) + 1) %k 2 2 + ------------------ - ---- n n 2 5 2 Example of linear recurrence with polynomial coefficients: (%i7) 2*x*(x+1)*y[x] - (x^2+3*x-2)*y[x+1] + (x-1)*y[x+2]; 2 (%o7) (x - 1) y - (x + 3 x - 2) y + 2 x (x + 1) y x + 2 x + 1 x (%i8) solve_rec(%, y[x], y[1]=1, y[3]=3); x 3 2 x! (%o9) y = ---- - -- x 4 2 Example of Ricatti type recurrence: (%i2) x*y[x+1]*y[x] - y[x+1]/(x+2) + y[x]/(x-1) = 0; y y x + 1 x (%o2) x y y - ------ + ----- = 0 x x + 1 x + 2 x - 1 (%i3) solve_rec(%, y[x], y[3]=5)$ (%i4) ratsimp(minfactorial(factcomb(%))); 3 30 x - 30 x (%o4) y = - ------------------------------------------------- x 6 5 4 3 2 5 x - 3 x - 25 x + 15 x + 20 x - 12 x - 1584 See also: `solve_rec_rat', `simplify_products', and `product_use_gamma'. There are also some inexact matches for `solve_rec'. Try `?? solve_rec' to see them.
Change History (9)
comment:1 Changed 11 years ago by
- Cc burcin added
comment:2 Changed 10 years ago by
- Cc kevin.stueve added
- Report Upstream set to N/A
comment:3 Changed 9 years ago by
- Cc kcrisman added
comment:4 Changed 9 years ago by
- Cc robert.marik added
comment:5 Changed 6 years ago by
- Cc eviatarbach added
comment:6 Changed 5 years ago by
- Cc rws added
comment:7 Changed 4 years ago by
- Description modified (diff)
comment:8 Changed 4 years ago by
- Description modified (diff)
comment:9 Changed 4 years ago by
- Cc ktkohl added
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