Re: Iterative application of FindRoot with adjusted started values

• To: mathgroup at smc.vnet.net
• Subject: [mg33026] Re: Iterative application of FindRoot with adjusted started values
• From: KIMIC Weijnitz Peter <micweij at eka.ericsson.se>
• Date: Tue, 26 Feb 2002 04:35:15 -0500 (EST)
• References: <a57hd0\$2kb\$1@smc.vnet.net> <a5cm4n\$9jj\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```About aes problem, maybe this is someting?

y[k_]:=y[k]= If[ k<2, k-1, a y[k-1] + b y[k-2] ];

Table[y[k],{k,1,5}]
gives:
{0, -b, -a b, -a^2b - b^2, -a b^2 + a(-a^2 b - b^2)}

Is this the expected result?

I have never used this kind of construction before but it is supposed to
be used
when you want to use old values without recalculating them.

Peter W

aes wrote:

>
> Me too.  More generally, I'd like to be able to use earlier ("already
> calculated"?) values in a table in calculating later values in the same table,
> e.g.
>
>    y = Table[ If[ k<2, k-1, a y[[k-1}] + b y[[k-2]] ], {k, 1, 5} ]
>
> but this doesn't work.
>
> [To handle things like this I resort to using a DO loop to calculate values of
> yTemp[k], then stuff these values into list y; but that's probably a naive --
> maybe even dumb? -- approach.]

```

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