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 > > > > > >