       Re: Composition of series

• To: mathgroup at smc.vnet.net
• Subject: [mg65350] Re: [mg65337] Composition of series
• From: "Carl K. Woll" <carlw at wolfram.com>
• Date: Tue, 28 Mar 2006 04:05:14 -0500 (EST)
• References: <200603271156.GAA04167@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Geico Caveman wrote:
> I am trying to compose two series with Mathematica :
>
> One is f1(x) = ...
>
> The other is x(y) = ...
>
> ComposeSeries quits complaining that the expansion point of the first series
> is different from the constant term of the second series
> (ComposeSeries::scmp). What I am really trying to do here is to express f
> (x) as a series in Log[x] (x is strictly greater than zero), so the second
> series is simply the series expansion of Exp[y].
>
> Mathematically, what is the problem with even attempting this operation ?
> Can't I replace x by log(z) in the first series, no matter what ?

Can't you just do:

f[Exp[y]]+O[y]^5 /. y->Log[x]

For example:

In:=
Sin[Exp[y]] + O[y]^3 /. y -> Log[x]

Out=
Sin+Cos Log[x]+1/2 (Cos-Sin) (Log[x])^2+(O[Log[x]])^3

Carl Woll
Wolfram Research

```

• Prev by Date: Re: Writing prime factor decomposision in conventional form
• Next by Date: Re: About subscripts
• Previous by thread: Composition of series
• Next by thread: Re: Composition of series