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Re: Parculiarities of FindRoot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116071] Re: Parculiarities of FindRoot
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Tue, 1 Feb 2011 06:51:45 -0500 (EST)

Limiting "func" to numeric input prevents FindRoot trying to use a  
symbolic one.

Clear[func]
func[y_?NumericQ] := Module[{x},
   x^2 /. FindRoot[x + y == 0, {x, 0.}]
   ]

func[.2]

0.04

FindRoot[func[z], {z, 0.}]

{z -> 0.}

Block also works, in place of Module.

Bobby

On Mon, 31 Jan 2011 02:24:17 -0600, Tianhui Li <tianhuil at princeton.edu>  
wrote:

> Here's a question for the group: in the following function, Func seems
> to evaluate numerical arguments correctly and *works* when you throw
> it into a FindRoot.  But the second command generates a lot of warning
> messages.  Does anyone understand why?
>
> Func[y_] := x^2 /. FindRoot[x + y == 0, {x, 0.}]
> Func[.2]
> FindRoot[Func[z], {z, 0.}]
>
> Warm Regards,
> Michael Li
> Bendheim Center for Finance
> Princeton University
> Princeton, NJ 08544
>


-- 
DrMajorBob at yahoo.com


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