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Re: Recursion

• To: mathgroup at smc.vnet.net
• Subject: [mg54965] Re: Recursion
• From: dh <dh at metrohm.ch>
• Date: Tue, 8 Mar 2005 05:03:51 -0500 (EST)
• References: <d0guu7$7jn$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hello Chris,
You are looking for a fix point of your function Wo.
The easiest way to do this is to use the function: FixedPoint (see  the 
help):
FixedPoint[Wo,startingvalue]
where Wo[x_Number] must return a number and startingvalue is a suitable 
numerical starting value.
However, this lets you not control the accuracy (only the max. number of 
steps) If you want control using the accuracy, use NestWhile.g.:

NestWhile[Wo, 0.1, (Abs[#1 - #2] > 10^-5) &, 2]
(see help)

good luck, Daniel

Christopher Grinde wrote:
> Hi. 
> I am quite new to mathematica and need help to set up a recursion loop:
>  
> 
> \!\(W\_0[T_] := \@\(\(\(12\ \[CurlyEpsilon]\_Si\)\/\(q\ a\)\) \(\(2\
> \(k\_B\) \
> T\)\/q\) Log[\(a\ W\_0[T]\)\/\(2\ n\_i[T]\)]\)\%3\)
> 
> How do I make this a recursive function which i can supply a start value for
> W0 and a limit for accuracy (W0[n]-W0[n+1]< some limit)
> 
> Any help would be highly appreciated