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Re: calculate Recurrence Equations

• To: mathgroup at smc.vnet.net
• Subject: [mg68755] Re: calculate Recurrence Equations
• From: "Mark Westwood" <markc.westwood at gmail.com>
• Date: Fri, 18 Aug 2006 03:11:59 -0400 (EDT)
• References: <ec1a1u$omo$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Frank

Check the section 2.5.9 in The Mathematica Book for an explanation of
this solution.  Modify your second definition to read:

anteil[n_] := anteil[n]=anteil[n - 1] + (anteil[n - 1]*5 - 1)/100

The effect of this is that the values of anteil[n] are stored when
first calculated, and not recalculated next time they are required.
You can see the effect by executing ?anteil after executing the
function.

On my PC anteil[30] runs in a second or so.

Regards
Mark Westwood

Frank Hechtner wrote:
> hi,
>
> i?m in trouble with my Recurrence Equations:
>
> i?ve defined the following function
>
> anteil[0] = 1
> anteil[n_] := anteil[n - 1] + (anteil[n - 1]*5 - 1)/100
>
> i want mathematica to calculate the values for anteil[30] and so on.
>
> Unfortunately mathematica needs for this calculation over 2 hours (and
> is still running, athlon x2 4600, 2 gb ram).
>
> I don?t see where are the difficulties for mathematica...
> 
> Thanx for your help
> 
> frank