import numpy as np
from astropy import units
from astropy.coordinates import FK4, FK5, SkyCoord
def _updateframe(frame: str | None) -> str:
"""Internal function to str frame to astropy frame.
Args:
frame (str): This should be one of 'J2000', 'B1950', 'FK5', 'FK4', and 'ICRS'.
Returns:
str: frame as is, FK5(equinox='J2000'), FK4(equinox='B1950'), or 'icrs'.
"""
if 'ICRS' in frame:
a = 'icrs'
elif 'J2000' in frame or 'FK5' in frame:
a = FK5(equinox='J2000')
elif 'B1950' in frame or 'FK4' in frame:
a = FK4(equinox='B1950')
elif isinstance(frame, str):
print(f'Unknown frame ({frame}) was found. Use ICRS instead.')
a = 'icrs'
else:
a = frame
return a
def _getframe(coord: str | list) -> tuple:
"""Internal function to pick up the frame name from the coordinates. When coord is a list, frame and framename are picked up from the first element.
Args:
coord (str): something like "J2000 01h23m45.6s 01d23m45.6s" or a list of them.
Returns:
tuple: updated coord and frame. frame is FK5(equinox='J2000), FK4(equinox='B1950'), or 'icrs'.
"""
def getframe_single(s: str) -> tuple:
c = s.split()
hasframe = len(c) == 3
hmsdms = f'{c[1]} {c[2]}' if hasframe else s
frame = _updateframe(c[0]) if hasframe else None
framename = c[0] if hasframe else None
return hmsdms, frame, framename
if isinstance(coord, str):
return getframe_single(coord)
else:
outlist = [getframe_single(c) for c in coord]
hmsdms = [a[0] for a in outlist]
frame = outlist[0][1]
framename = outlist[0][2]
return hmsdms, frame, framename
[docs]
def coord2xy(coords: str | list, coordorg: str = '00h00m00s 00d00m00s',
frame: str | None = None, frameorg: str | None = None,
) -> np.ndarray:
"""Transform R.A.-Dec. to relative (deg, deg).
Args:
coords (str, list): something like '01h23m45.6s 01d23m45.6s'. The input can be a list of str in an arbitrary shape.
coordorg (str, optional): something like '01h23m45.6s 01d23m45.6s'. The origin of the relative (deg, deg). Defaults to '00h00m00s 00d00m00s'.
frame (str, optional): coordinate frame. Defaults to None.
frameorg (str, optional): coordinate frame of the origin. Defaults to None.
Returns:
np.ndarray: [(array of) alphas, (array of) deltas] in degree. The shape of alphas and deltas is the input shape. With a single input, the output is [alpha0, delta0].
"""
coordorg, frameorg_in, _ = _getframe(coordorg)
frameorg = frameorg_in if frameorg is None else _updateframe(frameorg)
coords, frame_in, _ = _getframe(coords)
frame = frame_in if frame is None else _updateframe(frame)
if frame is None:
frame = frameorg
elif frameorg is None:
frameorg = frame
c0 = SkyCoord(coordorg, frame=frameorg) # frame=None means ICRS.
if frame is not None:
c0 = c0.transform_to(frame=frame)
clist = SkyCoord(coords, frame=frame) # frame=None means ICRS.
xy = c0.spherical_offsets_to(clist)
xy = np.array([xy[0].degree, xy[1].degree])
return xy
[docs]
def xy2coord(xy: list, coordorg: str = '00h00m00s 00d00m00s',
frame: str | None = None, frameorg: str | None = None,
) -> str | np.ndarray:
"""Transform relative (deg, deg) to R.A.-Dec.
Args:
xy (list): [(array of) alphas, (array of) deltas] in degree. alphas and deltas can have an arbitrary shape.
coordorg (str): something like '01h23m45.6s 01d23m45.6s'. The origin of the relative (deg, deg). Defaults to '00h00m00s 00d00m00s'.
frame (str): coordinate frame. Defaults to None.
frameorg (str): coordinate frame of the origin. Defaults to None.
Returns:
str: something like '01h23m45.6s 01d23m45.6s'. With multiple inputs, the output has the input shape.
"""
coordorg, frameorg_in, framenameorg = _getframe(coordorg)
frameorg = frameorg_in if frameorg is None else _updateframe(frameorg)
framename = framenameorg if frame is None else frame
frame = frameorg if frame is None else _updateframe(frame)
c0 = SkyCoord(coordorg, frame=frameorg) # frame=None means ICRS.
coords = c0.spherical_offsets_by(*xy * units.degree)
if frame is not None:
coords = coords.transform_to(frame=frame)
coords = coords.to_string('hmsdms')
if framename is not None:
if isinstance(coords, str):
coords = f'{framename} {coords}'
else:
coords = np.array([f'{framename} {s}' for s in coords])
return coords
[docs]
def rel2abs(xrel: float, yrel: float,
x: np.ndarray, y: np.ndarray) -> np.ndarray:
"""Transform relative coordinates to absolute ones.
Args:
xrel (float): 0 <= xrel <= 1. 0 and 1 correspond to x[0] and x[-1], respectively. Arbitrary shape.
yrel (float): same as xrel.
x (np.ndarray): [x0, x0+dx, x0+2dx, ...]
y (np.ndarray): [y0, y0+dy, y0+2dy, ...]
Returns:
np.ndarray: [xabs, yabs]. Each has the input's shape.
"""
xabs = (1. - xrel)*x[0] + xrel*x[-1]
yabs = (1. - yrel)*y[0] + yrel*y[-1]
return np.array([xabs, yabs])
[docs]
def abs2rel(xabs: float, yabs: float,
x: np.ndarray, y: np.ndarray) -> np.ndarray:
"""Transform absolute coordinates to relative ones.
Args:
xabs (float): In the same frame of x.
yabs (float): In the same frame of y.
x (np.ndarray): [x0, x0+dx, x0+2dx, ...]
y (np.ndarray): [y0, y0+dy, y0+2dy, ...]
Returns:
ndarray: [xrel, yrel]. Each has the input's shape. 0 <= xrel, yrel <= 1. 0 and 1 correspond to x[0] and x[-1], respectively.
"""
xrel = (xabs - x[0]) / (x[-1] - x[0])
yrel = (yabs - y[0]) / (y[-1] - y[0])
return np.array([xrel, yrel])
[docs]
def get_sec(coord: str, mode: str) -> str:
"""Pick up the second number from a hmsdms string.
Args:
coord (str): hmsdms string.
mode (str): 'ra' or 'dec'
Returns:
str: The second number as a string without the unit.
"""
i_axis = 0 if mode == 'ra' else 1
return coord.split(' ')[i_axis].split('m')[1].strip('s')
[docs]
def get_min(coord: str, mode: str) -> str:
"""Pick up the minute number from a hmsdms string.
Args:
coord (str): hmsdms string.
mode (str): 'ra' or 'dec'
Returns:
str: The minute number as a string without the unit.
"""
i_axis = 0 if mode == 'ra' else 1
s = 'h' if mode == 'ra' else 'd'
return coord.split(' ')[i_axis].split(s)[1].split('m')[0]
[docs]
def get_hmdm(coord: str, mode: str) -> str:
"""Pick up the coordinate string before the second part from a hsmdms string.
Args:
coord (str): hmsdms string.
mode (str): 'ra' or 'dec'
Returns:
str: The hm or dm string with the units.
"""
i_axis = 0 if mode == 'ra' else 1
return coord.split(' ')[i_axis].split('m')[0] + 'm'