Re: FindRoot, suppressing complex interval-numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg70923] Re: FindRoot, suppressing complex interval-numbers*From*: "dimitris" <dimmechan at yahoo.com>*Date*: Wed, 1 Nov 2006 03:56:39 -0500 (EST)*References*: <ei4lgf$dgg$1@smc.vnet.net>

I don't see any point to your example. Sin[x]+2=0 does not have any real roots. Anyway xs = {}; Block[{Message}, FindRoot[Sin[x] + 2, {x, 1.656*10^8, 1.653*10^8, 1.658*10^8}, EvaluationMonitor :> AppendTo[xs, x]]] {x -> 1.6560000109316254*^8} Cases[xs, _Complex] {} FindRoot works with Complex Numbers if you tell it to do so. Copy/Paste in a notebook and execute the following cell to see more FrontEndExecute[{HelpBrowserLookup["MainBook", "3.9.6", "6.7"]}] Here are also two very informative links for FindRoot within this forum http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_thread/thread/2587d839a40223bb/1a2c1c290d3c4b26?lnk=st&q=FindRoot&rnum=1#1a2c1c290d3c4b26 http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_thread/thread/9836d5644ef5b0a1/990d325c2340ea2a?lnk=st&q=FindRoot&rnum=2&hl=en#990d325c2340ea2a Regards Dimitris Paul wrote: > Hello, > I have the following problem: > Take the simple example > > FindRoot[Sin[x] +2, {x, 1.656 10^8, 1.653 10^8, 1.658 10^8}, > EvaluationMonitor :> AppendTo[xs, x]] > > In the Help we can read: "FindRoot[lhs==rhs, {x, a, a_min, a_max}] > searches for a solution, stopping the search if x ever gets outside the > range a_min to a_max. " > > But when I display xs I can see, that there are also two complex > numbers used. > > This is a problem if I use a function (in my case a compiled one) > inside FindRoot, which only accepts real numbers. > > So how can I suppress the using of complex numbers in FindRoot? > > Best regards, > Paul > > (Mathematica 5.2)