Problem with function definition inside DynamicModule

• To: mathgroup at smc.vnet.net
• Subject: [mg130344] Problem with function definition inside DynamicModule
• From: "Kevin J. McCann" <kjm at KevinMcCann.com>
• Date: Wed, 3 Apr 2013 22:52:17 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Delivered-to: l-mathgroup@wolfram.com
• Delivered-to: mathgroup-newout@smc.vnet.net
• Delivered-to: mathgroup-newsend@smc.vnet.net

```I am trying to write a dynamic module that does a polynomial fit with
different orders of the polynomial. I define f[x], the fit within the
module, but it does not update. If I try a delayed equals in the
definition, I get lots of unpleasant error messages. Any help would be
appreciated.

Thanks,

Kevin

data = Table[{x, x^2 + RandomReal[{-1, 1}]}, {x, 0, 5}];

datafit[dat_?ListQ] :=
DynamicModule[{m, d, f, x, y, k, n = 1, p1, powers},
p1 = ListPlot[dat, Joined -> False,
PlotStyle -> {Red, AbsolutePointSize[7]}, PlotRange -> All];

(* Here is where I think the problem is *)
f[x_] = Fit[dat, Table[x^k, {k, 0, n}], x];

Panel[
Column[
{
Row[{"n", Spacer[5], SetterBar[Dynamic[n], Range[5]]}],
Dynamic@
Plot[f[x], {x, 0, 5}, Epilog -> p1[[1]],
PlotLabel -> "n = " <> ToString[n],
PlotRange -> {0, 30}]
}
](*Column*)
](*Panel*)
]

datafit[data]

```

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