StoppingTest options (need help)

*To*: mathgroup at smc.vnet.net*Subject*: [mg72400] StoppingTest options (need help)*From*: Cham <martin465 at sympatico.ca>*Date*: Mon, 25 Dec 2006 04:52:28 -0500 (EST)

I'm using the NDSolve command to find a closed curve (it's a magnetic field line). It works, but I need to end the calculation at a specific point in space, so I don't get a curve with many turns. I only want a single turn to draw a complete loop. How can I use the StoppingTest options to tell Mathematica to find a single turn loop ? The specific code is like this : NDSolve[ { x'[t] == Bx[x[t], y[t], z[t]], y'[t] == By[x[t], y[t], z[t]], z'[t] == Bz[x[t], y[t], z[t]], x[0] == 0, y[0] == 1, z[0] == 0, }, {x, y, z}, {t, 0, 100}, StoppingTest -> ( ? ? ? )] Suppose I want the curve to stop at coordinates {x, y, z} = {1, 2, 3}, or better, I want it to be a complete loop with a single turn (stop when it's back at the initial coordinates). How can I tell that to Mathematica ?