any Python equivalent of Math::Polynomial::Solve?

Alex Renelt renelt at web.de
Thu Mar 3 20:28:39 CET 2005


Raymond L. Buvel wrote:
> Alex Renelt wrote:
> 
>> Alex Renelt wrote:
>>
>>> in addition:
>>> I'm writing a class for polynomial manipulation. The generalization 
>>> of the above code is:
>>>
>>> definitions:
>>> 1.) p = array([a_0, a_i, ..., a_n]) represents your polynomial
>>> P(x) = \sum _{i=0} ^n a_i x^i
>>>
>>> 2.) deg(p) is its degree
>>>
>>> 3.) monic(p) makes P monic, i.e. monic(p) = p / p[:-1]
>>>
>>> then you get:
>>> from numarray import *
>>> import numarray.linear_algebra as la
>>>
>>> def roots(p):
>>>     p = monic(p); n = deg(p)
>>>     M = asarray(zeros((n,n)), typecode = 'f8')
>>> # or 'c16' if you need complex coefficients
>>>     M[:-1,1:] = identity(n-1)
>>>     M[-1,:] = -p[:-1]
>>>     return la.eigenvalues(M)
>>>
>>> Alex
>>
>>
>>
>> uhh, I made a mistake:
>> under definitions, 3.)
>> its "monic(p) = p / p[-1]" of course
>>
>> Alex
> 
> 
> Alex,
> 
> If you want a class for polynomial manipulation, you should check out my 
> ratfun module.
> 
> http://calcrpnpy.sourceforge.net/ratfun.html
> 
> Ray

Ray,

thanks a lot for your hint but I'm writing it for a students paper in a 
german math class so I believe I should better do some work alone ;-)

In addition I only need a class for polynomials and not for rational 
functions and I'm testing different iterative polynomial solvers. So I'm 
happy to have my own small class which I understand 100%.

Generally I'm against rediscovering the wheel again and again!

Alex



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