Re: FindRoot
- To: mathgroup at smc.vnet.net
- Subject: [mg31495] Re: FindRoot
- From: <emueller at ybkim.mps.ohio-state.edu>
- Date: Thu, 8 Nov 2001 04:54:39 -0500 (EST)
- Organization: Ohio State University
- References: <9sb3u5$8oc$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Your function f takes on the value True if x equals i, and False if x does
not equal i. FindRoot acts on real valued functions. You get an error
message because neither True, nor False is a real number.
My guess is you want something like
f[i_] := x-i
which vanishes when x=i.
Cheers,
Erich
On Wed, 7 Nov 2001 Pieter-Jan.DeSmet at fys.kuleuven.ac.be wrote:
> Dear Sir,
>
> Can you clarify the following error message?
>
> In[3]:= f[i_] := x == i
>
> In[5]:= FindRoot[f[1], {x, 0}]
>
> FindRoot::frnum: Function {False} is not a length 1 list of
> numbers at {x} = {0.}.
>
> Out[5]=FindRoot[f[1], {x, 0}]
>
>
> This is a simplified version of an error message I got in a more
> difficult case. I hope that I have not made a stupid mistake.
>
> Thank you very much
>
> Pieter-Jan De Smet
>
>
>
>
>
>