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MathGroup Archive 2007

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Re: Evaluate, Replace, and Hold

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77181] Re: Evaluate, Replace, and Hold
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 5 Jun 2007 06:45:42 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <f40gib$65a$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

and
model = a x + b;
p1 = {a -> 1, b -> 0};
p2 = {a -> 1, b -> 1};

pts = Range[10];

f[pts_, param_] := With[{ff = Function[{x}, #] & @ (model /. param)},
   ff /@ pts
   ]

will do it.

Regards
   Jens

grenander at gmail.com wrote:
> This is a newbie question. I have a parametric form of a model and I
> would like to evaluate it with different parameters on a list of
> values.
> 
> model = a x + b;
> 
> Different sets of parameters:
> 
> p1 = {a->1, b->0};
> p2 = {a->1, b->1};
> 
> x for which I'd like to evaluate the model:
> 
> pts = Range[10];
> 
> I would like to define a function to evaluate the model at pts using
> any of the sets of paramters:
> 
> f[pts, p1]
> f[pts, p2]
> 
> I would also like it to work for single points:
> 
> f[1, p1]
> f[2, p1]
> 
> I've tried various forms for a function definition that dont work. I
> can do the following for a particular set of parameters:
> 
> Function[{x}, Evaluate[model /. p1]] /@ pts
> 
> but how can I turn it into a function of also the parameters. The
> below doesn't work, for example:
> 
> f[pts_, p_]:=Function[{x}, Evaluate[model /. p] ] /@ pts
> 
> What I know is from descending the documentation tree (v6.0) starting
> from the examples in FindFit. I have a fundamental misunderstanding of
> replacement rules and delayed evaluation.
> 
> Thanks.
> 
> 


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