phases=getphase(time,period=period,pdot=pdot,pddot=pddot, $
                     freq=nu,nudot=nudot,nuddot=nuddot,numpulse=numpulse, $
                     time0=time0,mjd=mjd)
 INPUTS:   time: array or scalar containing the times for which the
                 phases are to be computed. seconds (days if mjd
                 keyword is set)

           period: pulse period (seconds)
           pdot, pddot: 1st and 2nd pulse period derivative
                   (optional)
           freq: frequency (Hz)
           nudot, nuddot: 1st and 2nd frequency derivative (Hz/Hz etc.)
           time0: epoch of the observations (default: time[0], same
                 units as time)

            numpulse: if set, the code returns the number of pulses
               since the epoch, if not set the code returns
               the pulse phase, normalized to [0,1[
             mjd: if set, then time ant time0 are in units of days

             the function returns the pulse phase or the number of
             pulses since the epoch, depending on the setting of the
             numpulse keyword

             none

             none

             none

             nopefully none.

       straightforward formulae, following from
          nu(t) = nu0 + nudot*t + 0.5 nudot*t^2
           P(t) = P0+pdot*t+0.5*pdot*t^2
       the phase is then
          phi = int_0^t nu(t) dt
          phi = int_0^t dt/P(t)
       the formula for phi used in the code is derived from a
       3rd order Taylor series of 1/P(t), see, e.g., Padmanabhan,
       Volume 2, eq 6.93.

 $Log: getphase.pro,v $
 Revision 1.3  2005/05/14 20:59:47  wilms
 added mjd keyword
 Revision 1.2  2004/09/13 15:51:42  wilms
 cosmetic change in evaluation of phi for the pdot<>0 case
 Revision 1.1  2004/09/07 17:15:43  wilms
 initial release

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