[Numpy-discussion] poly class question

Charles R Harris charlesr.harris@gmail....
Fri Oct 2 13:09:32 CDT 2009


On Fri, Oct 2, 2009 at 11:35 AM, Charles R Harris <charlesr.harris@gmail.com
> wrote:

>
>
> On Fri, Oct 2, 2009 at 11:33 AM, Charles R Harris <
> charlesr.harris@gmail.com> wrote:
>
>>
>>
>> On Fri, Oct 2, 2009 at 11:30 AM, Charles R Harris <
>> charlesr.harris@gmail.com> wrote:
>>
>>>
>>>
>>> On Fri, Oct 2, 2009 at 11:08 AM, <josef.pktd@gmail.com> wrote:
>>>
>>>> Is there a way in numpy (or scipy) to get an infinite expansion for
>>>> the inverse of a polynomial (for a finite number of terms)
>>>>
>>>> np.poly1d([ -0.8, 1])**(-1)
>>>>
>>>> application for example the MA representation of an AR(1)
>>>>
>>>>
>>> Hmm, I've been working on a chebyshev class and division of a scalar by a
>>> chebyshev series is
>>> expressly forbidden, but it could be included if a good interface is
>>> proposed. Same would go for polynomials.
>>>
>>
>> In fact is isn't hard to get, for poly1d you should be able to multiply
>> the series by a power of x to shift it left, then divide.
>>
>>
> That is, divide a power of x by the polynomial.
>
>
You will also need to reverse the denominator coefficients...Chuck
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