  We further explored the radius-to-frequency mapping in cases of FRBs. An
analytical treatment of Lyutikov (2020) is presented. The frequency dependence
of the drifting rate and the drifting timescale are obtained. The aberration
effect and the twist of the magnetic field lines may result in drifting in both
directions. For one FRB, the burst width is larger at lower frequency according
to the radius-to-frequency mapping. For the FRB population, the magnetic fields
of the repeaters may be larger than that of the non-repeaters. Then, according
to the radius-to-frequency mapping, the burst widths of the repeaters will be
wider than that of the apparent non-repeaters. If similar window function (or
emission cones) like that of pulsars and magnetars is also at work in the case
of FRBs, then the window function may explain the single or multiple components
of FRB profiles. The radius-to-frequency mapping modeling is to some degree
independent of the underlying radio emission mechanism.
