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#===========================================================================
#
# Epoch
#
#===========================================================================
"""Epoch module."""
#===========================================================================
# Place all imports after here.
#
import math
import datetime as DT
from matplotlib.dates import date2num
#
# Place all imports before here.
#===========================================================================
#===========================================================================
class Epoch:
# Frame conversion offsets in seconds
# t(TO) = t(FROM) + allowed[ FROM ][ TO ]
allowed = {
"ET" : {
"UTC" : +64.1839,
},
"UTC" : {
"ET" : -64.1839,
},
}
#-----------------------------------------------------------------------
def __init__( self, frame, sec=None, jd=None, daynum=None, dt=None ):
"""Create a new Epoch object.
Build an epoch 1 of 2 ways:
Using seconds past a Julian date:
# Epoch( 'ET', sec=1e8, jd=2451545 )
or using a matplotlib day number
# Epoch( 'ET', daynum=730119.5 )
= ERROR CONDITIONS
- If the input units are not in the allowed list, an error is thrown.
= INPUT VARIABLES
- frame The frame of the epoch. Must be 'ET' or 'UTC'
- sec The number of seconds past the input JD.
- jd The Julian date of the epoch.
- daynum The matplotlib day number of the epoch.
- dt A python datetime instance.
"""
if ( ( sec is None and jd is not None ) or
( sec is not None and jd is None ) or
( daynum is not None and ( sec is not None or jd is not None ) ) or
( daynum is None and dt is None and ( sec is None or jd is None ) ) or
( daynum is not None and dt is not None ) or
( dt is not None and ( sec is not None or jd is not None ) ) or
( (dt is not None) and not isinstance(dt, DT.datetime) ) ):
msg = "Invalid inputs. Must enter sec and jd together, " \
"daynum by itself, or dt (must be a python datetime).\n" \
"Sec = %s\nJD = %s\ndnum= %s\ndt = %s" \
% ( str( sec ), str( jd ), str( daynum ), str( dt ) )
raise ValueError( msg )
if frame not in self.allowed:
msg = "Input frame '%s' is not one of the supported frames of %s" \
% ( frame, str( self.allowed.keys() ) )
raise ValueError( msg )
self._frame = frame
if dt is not None:
daynum = date2num( dt )
if daynum is not None:
# 1-JAN-0001 in JD = 1721425.5
jd = float( daynum ) + 1721425.5
self._jd = math.floor( jd )
self._seconds = ( jd - self._jd ) * 86400.0
else:
self._seconds = float( sec )
self._jd = float( jd )
# Resolve seconds down to [ 0, 86400 )
deltaDays = int( math.floor( self._seconds / 86400.0 ) )
self._jd += deltaDays
self._seconds -= deltaDays * 86400.0
#-----------------------------------------------------------------------
def convert( self, frame ):
if self._frame == frame:
return self
offset = self.allowed[ self._frame ][ frame ]
return Epoch( frame, self._seconds + offset, self._jd )
#-----------------------------------------------------------------------
def frame( self ):
return self._frame
#-----------------------------------------------------------------------
def julianDate( self, frame ):
t = self
if frame != self._frame:
t = self.convert( frame )
return t._jd + t._seconds / 86400.0
#-----------------------------------------------------------------------
def secondsPast( self, frame, jd ):
t = self
if frame != self._frame:
t = self.convert( frame )
delta = t._jd - jd
return t._seconds + delta * 86400
#-----------------------------------------------------------------------
def __cmp__( self, rhs ):
"""Compare two Epoch's.
= INPUT VARIABLES
- rhs The Epoch to compare against.
= RETURN VALUE
- Returns -1 if self < rhs, 0 if self == rhs, +1 if self > rhs.
"""
t = self
if self._frame != rhs._frame:
t = self.convert( rhs._frame )
if t._jd != rhs._jd:
return cmp( t._jd, rhs._jd )
return cmp( t._seconds, rhs._seconds )
#-----------------------------------------------------------------------
def __add__( self, rhs ):
"""Add a duration to an Epoch.
= INPUT VARIABLES
- rhs The Epoch to subtract.
= RETURN VALUE
- Returns the difference of ourselves and the input Epoch.
"""
t = self
if self._frame != rhs.frame():
t = self.convert( rhs._frame )
sec = t._seconds + rhs.seconds()
return Epoch( t._frame, sec, t._jd )
#-----------------------------------------------------------------------
def __sub__( self, rhs ):
"""Subtract two Epoch's or a Duration from an Epoch.
Valid:
Duration = Epoch - Epoch
Epoch = Epoch - Duration
= INPUT VARIABLES
- rhs The Epoch to subtract.
= RETURN VALUE
- Returns either the duration between to Epoch's or the a new
Epoch that is the result of subtracting a duration from an epoch.
"""
# Delay-load due to circular dependencies.
import matplotlib.testing.jpl_units as U
# Handle Epoch - Duration
if isinstance( rhs, U.Duration ):
return self + -rhs
t = self
if self._frame != rhs._frame:
t = self.convert( rhs._frame )
days = t._jd - rhs._jd
sec = t._seconds - rhs._seconds
return U.Duration( rhs._frame, days*86400 + sec )
#-----------------------------------------------------------------------
def __str__( self ):
"""Print the Epoch."""
return "%22.15e %s" % ( self.julianDate( self._frame ), self._frame )
#-----------------------------------------------------------------------
def __repr__( self ):
"""Print the Epoch."""
return str( self )
#-----------------------------------------------------------------------
def range( start, stop, step ):
"""Generate a range of Epoch objects.
Similar to the Python range() method. Returns the range [
start, stop ) at the requested step. Each element will be a
Epoch object.
= INPUT VARIABLES
- start The starting value of the range.
- stop The stop value of the range.
- step Step to use.
= RETURN VALUE
- Returns a list contianing the requested Epoch values.
"""
elems = []
i = 0
while True:
d = start + i * step
if d >= stop:
break
elems.append( d )
i += 1
return elems
range = staticmethod( range )
#===========================================================================