Re: FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg31484] Re: [mg31463] FindRoot*From*: Mianlai Zhou <lailai at nikhef.nl>*Date*: Thu, 8 Nov 2001 04:54:19 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, It is because that FindRoot has an attribute HoldAll, i.e., it will not evaluate its arguments until it starts to try to find the roots (replacing x by number). Therefore, you have to change as follows to get what you want: In[5]:= FindRoot[Evaluate @ f[1], {x, 0}] Good luck! Mianlai Zhou Theory Group, NIKHEF Amsterdam, the Netherlands 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 > > > >