Re: [Reduce-algebra-developers] Accessing coefficients of a Taylor series

[Alan B. <ala...@gm...>]

Arthur has already replied regarding accessing coefficients of a power 
series built with the Taylor package.

For series built with the TPS package, there is a slightly more direct 
way, for example:

load tps;
s := ps(sin x, x, 0);
psterm(s,9);

One may also use pstruncate to truncate a power series after a specified 
number of terms and then usecoeff orcoeffn to extract the coefficient(s) 
of the the desired term(s) as Arthur indicated.

Sections 16.1 & 16.2 of the manual give more info about the facilities 
of the two packages and give a brief discussion of the relative 
advantages/disadvantages of the two systems.

Alan Barnes

On 10/09/2022 18:36, Thomas Baruchel wrote:
> Hi,
>
> what is the most reliable way of accessing coefficients of a power 
> series (built with the taylor() function)?
>
> I initially had some success with "part", but as soon as some 
> coefficnets are zero, the "part" function returns wrong terms.
>
> Also, I am only interested in the coefficient, not the variable; for 
> insance, for   1 + 2*x - 3*x^2 + O(x^3), I would like to get the -3 
> coefficient for degree 2 rather than the whole -3*x^2 term.
>
> Thank you by advance,
>
> best regards,
>
> -- 
> Thomas Baruchel
>
>
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