  We report observations of the formation and subsequent decay of a vortex
lattice in a Bose-Einstein condensate confined in a hybrid optical-magnetic
trap. Vortices are induced by rotating the anharmonic magnetic potential that
provides confinement in the horizontal plane. We present simple numerical
techniques based on image analysis to detect vortices and analyze their
distributions. We use these methods to quantify the amount of order present in
the vortex distribution as it transitions from a disordered array to the
energetically favorable ordered lattice.
