Re: Parculiarities of FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg116082] Re: Parculiarities of FindRoot*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Tue, 1 Feb 2011 06:53:50 -0500 (EST)

On 1/31/11 at 3:24 AM, tianhuil at princeton.edu (Tianhui Li) 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.}] FindRoot is a *numeric* root finder. When you do Func[.2] you provide a numeric value and FindRoot can find a numeric solution. When you do FindRoot[z] you are supplying a symbolic value and it is not possible for FindRoot to get a numeric solution.