def calc_time(lower_bound, upper_bound, location, attribute, value,
pressure=101325, temperature=12, xtol=1.0e-12):
"""
Calculate the time between lower_bound and upper_bound
where the attribute is equal to value. Uses PyEphem for
solar position calculations.
Parameters
----------
lower_bound : datetime.datetime
upper_bound : datetime.datetime
location : pvlib.Location object
attribute : str
The attribute of a pyephem.Sun object that
you want to solve for. Likely options are 'alt'
and 'az' (which must be given in radians).
value : int or float
The value of the attribute to solve for
pressure : int or float, optional
Air pressure in Pascals. Set to 0 for no
atmospheric correction.
temperature : int or float, optional
Air temperature in degrees C.
xtol : float, optional
The allowed error in the result from value
Returns
-------
datetime.datetime
Raises
------
ValueError
If the value is not contained between the bounds.
AttributeError
If the given attribute is not an attribute of a
PyEphem.Sun object.
"""
try:
import scipy.optimize as so
except ImportError:
raise ImportError('The calc_time function requires scipy')
obs, sun = _ephem_setup(location, pressure, temperature)
def compute_attr(thetime, target, attr):
obs.date = thetime
sun.compute(obs)
return getattr(sun, attr) - target
lb = datetime_to_djd(lower_bound)
ub = datetime_to_djd(upper_bound)
djd_root = so.brentq(compute_attr, lb, ub,
(value, attribute), xtol=xtol)
return djd_to_datetime(djd_root, location.tz)
def calc_time(lower_bound,
upper_bound,
latitude,
longitude,
attribute,
value,
altitude=0,
pressure=101325,
temperature=12,
horizon='+0:00',
xtol=1.0e-12):
"""
Calculate the time between lower_bound and upper_bound
where the attribute is equal to value. Uses PyEphem for
solar position calculations.
Parameters
----------
lower_bound : datetime.datetime
upper_bound : datetime.datetime
latitude : float
longitude : float
attribute : str
The attribute of a pyephem.Sun object that
you want to solve for. Likely options are 'alt'
and 'az' (which must be given in radians).
value : int or float
The value of the attribute to solve for
altitude : float, default 0
Distance above sea level.
pressure : int or float, optional, default 101325
Air pressure in Pascals. Set to 0 for no
atmospheric correction.
temperature : int or float, optional, default 12
Air temperature in degrees C.
horizon : string, optional, default '+0:00'
arc degrees:arc minutes from geometrical horizon for sunrise and
sunset, e.g., horizon='+0:00' to use sun center crossing the
geometrical horizon to define sunrise and sunset,
horizon='-0:34' for when the sun's upper edge crosses the
geometrical horizon
xtol : float, optional, default 1.0e-12
The allowed error in the result from value
Returns
-------
datetime.datetime
Raises
------
ValueError
If the value is not contained between the bounds.
AttributeError
If the given attribute is not an attribute of a
PyEphem.Sun object.
"""
try:
import scipy.optimize as so
except ImportError:
raise ImportError('The calc_time function requires scipy')
obs, sun = _ephem_setup(latitude, longitude, altitude, pressure,
temperature, horizon)
def compute_attr(thetime, target, attr):
obs.date = thetime
sun.compute(obs)
return getattr(sun, attr) - target
lb = datetime_to_djd(lower_bound)
ub = datetime_to_djd(upper_bound)
djd_root = so.brentq(compute_attr, lb, ub, (value, attribute), xtol=xtol)
return djd_to_datetime(djd_root)
def calc_time(lower_bound,
upper_bound,
location,
attribute,
value,
pressure=101325,
temperature=12,
xtol=1.0e-12):
"""
Calculate the time between lower_bound and upper_bound
where the attribute is equal to value. Uses PyEphem for
solar position calculations.
Parameters
----------
lower_bound : datetime.datetime
upper_bound : datetime.datetime
location : pvlib.Location object
attribute : str
The attribute of a pyephem.Sun object that
you want to solve for. Likely options are 'alt'
and 'az' (which must be given in radians).
value : int or float
The value of the attribute to solve for
pressure : int or float, optional
Air pressure in Pascals. Set to 0 for no
atmospheric correction.
temperature : int or float, optional
Air temperature in degrees C.
xtol : float, optional
The allowed error in the result from value
Returns
-------
datetime.datetime
Raises
------
ValueError
If the value is not contained between the bounds.
AttributeError
If the given attribute is not an attribute of a
PyEphem.Sun object.
"""
try:
import scipy.optimize as so
except ImportError:
raise ImportError('The calc_time function requires scipy')
obs, sun = _ephem_setup(location, pressure, temperature)
def compute_attr(thetime, target, attr):
obs.date = thetime
sun.compute(obs)
return getattr(sun, attr) - target
lb = datetime_to_djd(lower_bound)
ub = datetime_to_djd(upper_bound)
djd_root = so.brentq(compute_attr, lb, ub, (value, attribute), xtol=xtol)
return djd_to_datetime(djd_root, location.tz)
def calc_time(lower_bound, upper_bound, latitude, longitude, attribute, value,
altitude=0, pressure=101325, temperature=12, horizon='+0:00',
xtol=1.0e-12):
"""
Calculate the time between lower_bound and upper_bound
where the attribute is equal to value. Uses PyEphem for
solar position calculations.
Parameters
----------
lower_bound : datetime.datetime
upper_bound : datetime.datetime
latitude : float
longitude : float
attribute : str
The attribute of a pyephem.Sun object that
you want to solve for. Likely options are 'alt'
and 'az' (which must be given in radians).
value : int or float
The value of the attribute to solve for
altitude : float, default 0
Distance above sea level.
pressure : int or float, optional, default 101325
Air pressure in Pascals. Set to 0 for no
atmospheric correction.
temperature : int or float, optional, default 12
Air temperature in degrees C.
horizon : string, optional, default '+0:00'
arc degrees:arc minutes from geometrical horizon for sunrise and
sunset, e.g., horizon='+0:00' to use sun center crossing the
geometrical horizon to define sunrise and sunset,
horizon='-0:34' for when the sun's upper edge crosses the
geometrical horizon
xtol : float, optional, default 1.0e-12
The allowed error in the result from value
Returns
-------
datetime.datetime
Raises
------
ValueError
If the value is not contained between the bounds.
AttributeError
If the given attribute is not an attribute of a
PyEphem.Sun object.
"""
try:
import scipy.optimize as so
except ImportError:
raise ImportError('The calc_time function requires scipy')
obs, sun = _ephem_setup(latitude, longitude, altitude,
pressure, temperature, horizon)
def compute_attr(thetime, target, attr):
obs.date = thetime
sun.compute(obs)
return getattr(sun, attr) - target
lb = datetime_to_djd(lower_bound)
ub = datetime_to_djd(upper_bound)
djd_root = so.brentq(compute_attr, lb, ub,
(value, attribute), xtol=xtol)
return djd_to_datetime(djd_root)
