  Transitions between the quantum Hall state and the Anderson insulator are
studied in a two dimensional tight binding model with a uniform magnetic field
and a random potential. By the string (anyon) gauge, the weak magnetic field
regime is explored numerically. The regime is closely related to the continuum
model. The change of the Hall conductance and the trajectoy of the delocalized
states are investigated by the topological arguments and the Thouless number
study.
