Calculates how many seconds it takes for the system to evolve from the initial frequency to final frequency , i.e. the ``duration'' of a chirp.

`f1`: Input. The initial frequency in Hertz.`f2`: Input. The final frequency in Hertz.`m1`: Input. The mass of the first body in units of the solar mass.`m2`: Input. The mass of the second body in units of the solar mass.- Return value: Output. The duration of the chirp in seconds or a value if an error occurred (if has not been calculated).

- Author: Serge Droz, droz@physics.uoguelph.ca
- Comments: You must have read in the data files and calculated for this to work.

Bruce Allen 2000-11-19