Re: Creation and evaluation of polynomials
- To: mathgroup at smc.vnet.net
- Subject: [mg89450] Re: Creation and evaluation of polynomials
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Tue, 10 Jun 2008 03:38:26 -0400 (EDT)
- Organization: Uni Leipzig
- References: <g2j05j$510$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
Hi,
imaging that *we* have no function that is able to create
the polynomial p^5 + 3p^2 from the invalid Mathematica
input.
All your ToString[]/ ToExpression[] is complete nonsense.
But imaging that
polynomial[lst_, var_: x] := Plus @@ MapIndexed[#1*var^(#2[[1]]-1) &, lst]
create a polynomial, than
D[polynomial[{1, 0, 0, 0, 1, 0, 1}], x]
compute the derivative
and
NSolve[polynomial[{0, 2, 1}] == x, x]
will find the numerical roots.
Regards
Jens
jmgomezgoo at gmail.com wrote:
> Hi!
>
> Image we have a function that create a Polynomial:
>
> polynomial[{1,0,0,0,1,0,1,}] -> p^5 + 3p^2
>
> And we want to calulate roots and the derivate of this polynomial.
>
> I try with ToString[polynomial[{1,0,0,0,1,0,1}]] in order to use
> convert the polynomial expression to string first and later use
>
> ToExpression[]
>
> and calculate roots
>
> D[ToExpression[ToString[polynomial[{1,0,0,0,1,0,1}]], x]
>
> like the next examples:
>
> D[ToExpression["x^2+2x"], x]
>
> or
>
> NSolve[ToExpression["x^2+2x==x"], x]
>
>
> But ToString erase ^ symbol.
>
> Somebody knows how to solve it?
>
>
> Warm regards
> -jm
>
>
>