Re: Re: Hold problems with FindRoot

• To: mathgroup at smc.vnet.net
• Subject: [mg57125] Re: [mg57073] Re: Hold problems with FindRoot
• From: Jonas Björnerstedt <lists at bjornerstedt.org>
• Date: Mon, 16 May 2005 21:35:23 -0400 (EDT)
• References: <428457A1.3020501@bjornerstedt.org> <200505140858.EAA09467@smc.vnet.net> <acbec1a405051410265918dd00@mail.gmail.com>
• Sender: owner-wri-mathgroup at wolfram.com

```Thanks! This solved my problem. Is this an undocumented restriction in
how FindRoot can be used, or where can I find more documentation?

Jonas

Chris Chiasson wrote:

>Try changing the definitions of f and g, via a PatternTest, so that
>they are only defined for numeric arguments.
>
>f[x_?NumericQ,y_?NumericQ]=blahblah1
>g[x_?NumericQ,y_?NumericQ]=blahblah2
>
>On 5/14/05, Jonas Björnerstedt <lists at bjornerstedt.org> wrote:
>
>
>>Hello again,
>>
>>There was a small mistake in my previous posting. It should have said:
>>
>>FindRoot[Evaluate[{f[x,y]==0, g[x,y]==0}],{{x,1},{y,1}}]
>>
>>where f and g are functions that work correctly. Trying to solve one
>>equation for two unknowns would cause other problems than I am currently
>>having.
>>
>>Jonas.
>>
>>Jonas Björnerstedt wrote:
>>
>>
>>
>>>Hello all,
>>>
>>>I have problems getting FindRoot to evaluate the equations it
>>>evaluates, despite using Evaluate on the equations. I have a rather
>>>complex function f[x,y] that works correctly with individual values x
>>>and y. Evaluating the following expression does not work however.
>>>
>>>FindRoot[Evaluate[f[x,y]==0],{{x,1},{y,1}}]
>>>
>>>When evaluating, I get similar errors as when I evaluate f without
>>>inserting values for x and y. I can also do a Plot3D on f without
>>>using Evaluate.
>>>
>>>Does anybody have an idea what the problem is?
>>>
>>>Jonas
>>>
>>>
>>>
>>
>>
>
>
>
>

```

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