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MathGroup Archive 2006

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Re: Beginner--[Please Help]How to get coefficient list issued from a Series Command

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70158] Re: Beginner--[Please Help]How to get coefficient list issued from a Series Command
  • From: albert <awnl at arcor.de>
  • Date: Fri, 6 Oct 2006 01:58:00 -0400 (EDT)
  • References: <eg2e8k$73m$1@smc.vnet.net>

abdou.oumaima at hotmail.com wrote:

> Greeting,
> 
> I've a list issued from power series like : K={a1+b1 x +c1 x^2 , a2+b2 x
> +c2 x^2, a3+b3 x +c3 x^2} I need te have a1, a2 and a3.
> Then b1,b2 and b3.
> And  c1,c2 and c3.

This gives all coefficients:

In[7]:= coeffs = Map[CoefficientList[#,x]&,K]
Out[7]=
{{a1, b1, c1}, {a2, b2, c2}, {a3, b3, c3}}

Transpose the resulting matrix to get the coefficients in the form you
indicated:

In[8]:= Transpose[coeffs]
Out[8]=
{{a1, a2, a3}, {b1, b2, b3}, {c1, c2, c3}}

> I need to use all those coefficients in a Sum Command. How to do that
> please?

I don't understand what you want to do, if you want to add all coefficients
for the same power of x you could do:

In[9]:= Map[Total,Transpose[coeffs]]
Out[9]=
{a1 + a2 + a3, b1 + b2 + b3, c1 + c2 + c3}

hth,

albert


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