Using FindRoot on a numerical vector-valued function
- To: mathgroup at smc.vnet.net
- Subject: [mg41123] Using FindRoot on a numerical vector-valued function
- From: Randall Beer <beer at eecs.cwru.edu>
- Date: Sun, 4 May 2003 03:55:25 -0400 (EDT)
- Organization: Case Western Reserve University, Cleveland, OH, USA
- Sender: owner-wri-mathgroup at wolfram.com
Suppose I have a function F that takes N arguments and returns a
length-N vector: F[1,2,3] => {-1.1,2.08,0.03}. This function involves
numerically computing an object and then returning certain components of
that object, so it cannot be expanded with symbolic arguments (e.g.,
F[x,y,z] will not work).
I need to find the arguments that make F return a vector of all 0s.
That is, I would like to do something like:
FindRoot[F[y1, y2, y3], {y1, -1, 1}, {y2, -1, 1}, {y3, -1, 1}]
Unfortunately, this doesn't work because FindRoot wants 3 things, not a
function returnning a vector of 3 things
I could do
FindRoot[{F1[y1, y2, y3] == 0, F2[y1, y2, y3] == 0, F3[y1, y2, y3] ==
0}, . . .]
but then I would have to numerically recompute the object 3 times.
Any suggestions would be greatly appreciated.