NAME:
rect_to_cyl_vec
PURPOSE:
transform vectors from rectangular to cylindrical coordinates vectors
INPUT:
vx -
vy -
vz -
X - X
Y - Y
Z - Z
cyl - if True, X,Y,Z are already cylindrical
OUTPUT:
vR,vT,vz
HISTORY:
2010-09-24 - Written - Bovy (NYU)