The problem is that the current problem with Poly breaks thinks which depend
on it. For us, it breaks calculation of eigenvalues...Is it possible to
exclude symbols which are not in the polynomial variable? Right now, it
seems to decompose all symbols....
Thanks,
William
On Thu, Jul 30, 2009 at 11:05 AM, Mateusz Paprocki <matt...@gmail.com>wrote:
> Hi,
>
> On Thu, Jul 30, 2009 at 07:43:43AM -0700, smichr wrote:
> >
> > > Would your routine help any for the expression in issue 1562?
> > > simplify() doesn't do anything to it because Poly.cancel() doesn't
> > > cancel the sin and cos terms. The same for factor.
> > >
> >
> > I'm happy to report that factor is able to do the heavy lifting after
> > you polify the expression you asked about in issue 1562:
> >
> > >>> x=var('x')
> > >>> eq=8*x**15*cos(x)**6*sin(x)**21/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) +
> 20*x**15*cos(x)**4*sin(x)**23/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) +
> 16*x**15*cos(x)**2*sin(x)**25/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) + 4*x**15*sin(x)**27/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23)
> > >>> repl,p=polify(eq)
> > >>> p
> > 4*x**15*x1**27/(-2*x**15*x0**2*x1**21 - x**15*x1**23) +
> > 8*x**15*x0**6*x1**21/(-2*x**15*x0**2*x1**21 - x**15*x1**23) +
> > 16*x**15*x0**2*x1**25/(-2*x**15*x0**2*x1**21 - x**15*x1**23) +
> > 20*x**15*x0**4*x1**23/(-2*x**15*x0**2*x1**21 - x**15*x1**23)
> > >>> n,d=p.as_numer_denom() #it's rational and factor won't work with that
> but...
> > >>> factor(n)/factor(d)
> > -4*(x0**2 + x1**2)**2
> > >>> _.subs(r)
> > -4*(cos(x)**2 + sin(x)**2)**2
> > >>> trigsimp(_)
> > -4
> >
> > The routine I've got just completely reduces the expression to symbols
> > with numerical coefficients and integer powers. I'm not sure where to
> > work this routine in. Perhaps it should go into the cse section since
> > it can (but doesn't right now) use cse to get close to the desired
> > expression and then just do clean up. It could also go into polys
> > module. It's more like the cse routine in that it gives you an
> > expression (that is more polynomial-like than cse) but it also gives
> > you the replacements that you have to carry around. I'm open to some
> > discussion.
> >
>
> support for polynomial-like expressions will be included in new version
> of polys module, so you should be just patient.
>
> In [1]: eq=8*x**15*cos(x)**6*sin(x)**21/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) +
> 20*x**15*cos(x)**4*sin(x)**23/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) +
> 16*x**15*cos(x)**2*sin(x)**25/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23) + 4*x**15*sin(x)**27/(-2*x**15*cos(x)**2*sin(x)**21 -
> x**15*sin(x)**23)
>
> In [2]: p, q = eq.as_numer_denom()
>
> In [3]: from sympy.polys.polytools import *
>
> In [4]: gcd, pp, qq = cofactors(p, q)
>
> In [5]: pp
> Out[5]:
> 2 2 4 4
> - 8⋅cos (x)⋅sin (x) - 4⋅cos (x) - 4⋅sin (x)
>
> In [6]: qq
> Out[6]: 1
>
> --
> Mateusz
>
>
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to sympy@googlegroups.com
To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sympy?hl=en
-~----------~----~----~----~------~----~------~--~---
