  We calculated numerically the localization length of one-dimensional Anderson
model with diagonal disorder. For weak disorder, we showed that the
localization length changes continuously as the energy changes from the band
center to the boundary of the anomalous region near the band edge. We found
that all the localization lengths for different disorder strengths and
different energies collapse onto a single curve, which can be fitted by a
simple equation. Thus the description of the perturbation theory and the band
center anomaly were unified into this equation.
