# Licensed under a 3-clause BSD style license - see LICENSE.rst
# This module implements the base NDData class.
from copy import deepcopy
import numpy as np
from astropy import log
from astropy.units import Quantity, Unit
from astropy.utils.metadata import MetaData
from astropy.wcs.wcsapi import (
BaseHighLevelWCS,
BaseLowLevelWCS,
HighLevelWCSWrapper,
SlicedLowLevelWCS,
)
from .nddata_base import NDDataBase
from .nduncertainty import NDUncertainty, UnknownUncertainty
__all__ = ["NDData"]
_meta_doc = """`dict`-like : Additional meta information about the dataset."""
[docs]class NDData(NDDataBase):
"""
A container for `numpy.ndarray`-based datasets, using the
`~astropy.nddata.NDDataBase` interface.
The key distinction from raw `numpy.ndarray` is the presence of
additional metadata such as uncertainty, mask, unit, a coordinate system
and/or a dictionary containing further meta information. This class *only*
provides a container for *storing* such datasets. For further functionality
take a look at the ``See also`` section.
See also: https://docs.astropy.org/en/stable/nddata/
Parameters
----------
data : `numpy.ndarray`-like or `NDData`-like
The dataset.
uncertainty : any type, optional
Uncertainty in the dataset.
Should have an attribute ``uncertainty_type`` that defines what kind of
uncertainty is stored, for example ``"std"`` for standard deviation or
``"var"`` for variance. A metaclass defining such an interface is
`NDUncertainty` - but isn't mandatory. If the uncertainty has no such
attribute the uncertainty is stored as `UnknownUncertainty`.
Defaults to ``None``.
mask : any type, optional
Mask for the dataset. Masks should follow the ``numpy`` convention that
**valid** data points are marked by ``False`` and **invalid** ones with
``True``.
Defaults to ``None``.
wcs : any type, optional
World coordinate system (WCS) for the dataset.
Default is ``None``.
meta : `dict`-like object, optional
Additional meta information about the dataset. If no meta is provided
an empty `collections.OrderedDict` is created.
Default is ``None``.
unit : unit-like, optional
Unit for the dataset. Strings that can be converted to a
`~astropy.units.Unit` are allowed.
Default is ``None``.
copy : `bool`, optional
Indicates whether to save the arguments as copy. ``True`` copies
every attribute before saving it while ``False`` tries to save every
parameter as reference.
Note however that it is not always possible to save the input as
reference.
Default is ``False``.
.. versionadded:: 1.2
psf : `numpy.ndarray` or None, optional
Image representation of the PSF. In order for convolution to be flux-
preserving, this should generally be normalized to sum to unity.
Raises
------
TypeError
In case ``data`` or ``meta`` don't meet the restrictions.
Notes
-----
Each attribute can be accessed through the homonymous instance attribute:
``data`` in a `NDData` object can be accessed through the `data`
attribute::
>>> from astropy.nddata import NDData
>>> nd = NDData([1,2,3])
>>> nd.data
array([1, 2, 3])
Given a conflicting implicit and an explicit parameter during
initialization, for example the ``data`` is a `~astropy.units.Quantity` and
the unit parameter is not ``None``, then the implicit parameter is replaced
(without conversion) by the explicit one and a warning is issued::
>>> import numpy as np
>>> import astropy.units as u
>>> q = np.array([1,2,3,4]) * u.m
>>> nd2 = NDData(q, unit=u.cm)
INFO: overwriting Quantity's current unit with specified unit. [astropy.nddata.nddata]
>>> nd2.data # doctest: +FLOAT_CMP
array([1., 2., 3., 4.])
>>> nd2.unit
Unit("cm")
See also
--------
NDDataRef
NDDataArray
"""
# Instead of a custom property use the MetaData descriptor also used for
# Tables. It will check if the meta is dict-like or raise an exception.
meta = MetaData(doc=_meta_doc, copy=False)
def __init__(
self,
data,
uncertainty=None,
mask=None,
wcs=None,
meta=None,
unit=None,
copy=False,
psf=None,
):
# Rather pointless since the NDDataBase does not implement any setting
# but before the NDDataBase did call the uncertainty
# setter. But if anyone wants to alter this behavior again the call
# to the superclass NDDataBase should be in here.
super().__init__()
# Check if data is any type from which to collect some implicitly
# passed parameters.
if isinstance(data, NDData): # don't use self.__class__ (issue #4137)
# Of course we need to check the data because subclasses with other
# init-logic might be passed in here. We could skip these
# tests if we compared for self.__class__ but that has other
# drawbacks.
# Comparing if there is an explicit and an implicit unit parameter.
# If that is the case use the explicit one and issue a warning
# that there might be a conflict. In case there is no explicit
# unit just overwrite the unit parameter with the NDData.unit
# and proceed as if that one was given as parameter. Same for the
# other parameters.
if unit is not None and data.unit is not None and unit != data.unit:
log.info("overwriting NDData's current unit with specified unit.")
elif data.unit is not None:
unit = data.unit
if uncertainty is not None and data.uncertainty is not None:
log.info(
"overwriting NDData's current "
"uncertainty with specified uncertainty."
)
elif data.uncertainty is not None:
uncertainty = data.uncertainty
if mask is not None and data.mask is not None:
log.info("overwriting NDData's current mask with specified mask.")
elif data.mask is not None:
mask = data.mask
if wcs is not None and data.wcs is not None:
log.info("overwriting NDData's current wcs with specified wcs.")
elif data.wcs is not None:
wcs = data.wcs
if psf is not None and data.psf is not None:
log.info("Overwriting NDData's current psf with specified psf.")
elif data.psf is not None:
psf = data.psf
if meta is not None and data.meta is not None:
log.info("overwriting NDData's current meta with specified meta.")
elif data.meta is not None:
meta = data.meta
data = data.data
else:
if hasattr(data, "mask") and hasattr(data, "data"):
# Separating data and mask
if mask is not None:
log.info(
"overwriting Masked Objects's current mask with specified mask."
)
else:
mask = data.mask
# Just save the data for further processing, we could be given
# a masked Quantity or something else entirely. Better to check
# it first.
data = data.data
if isinstance(data, Quantity):
if unit is not None and unit != data.unit:
log.info("overwriting Quantity's current unit with specified unit.")
else:
unit = data.unit
data = data.value
# Quick check on the parameters if they match the requirements.
if (
not hasattr(data, "shape")
or not hasattr(data, "__getitem__")
or not hasattr(data, "__array__")
):
# Data doesn't look like a numpy array, try converting it to
# one.
data = np.array(data, subok=True, copy=False)
# Another quick check to see if what we got looks like an array
# rather than an object (since numpy will convert a
# non-numerical/non-string inputs to an array of objects).
if data.dtype == "O":
raise TypeError("could not convert data to numpy array.")
if unit is not None:
unit = Unit(unit)
if copy:
# Data might have been copied before but no way of validating
# without another variable.
data = deepcopy(data)
mask = deepcopy(mask)
wcs = deepcopy(wcs)
psf = deepcopy(psf)
meta = deepcopy(meta)
uncertainty = deepcopy(uncertainty)
# Actually - copying the unit is unnecessary but better safe
# than sorry :-)
unit = deepcopy(unit)
# Store the attributes
self._data = data
self.mask = mask
self._wcs = None
if wcs is not None:
# Validate the wcs
self.wcs = wcs
self.meta = meta # TODO: Make this call the setter sometime
self._unit = unit
# Call the setter for uncertainty to further check the uncertainty
self.uncertainty = uncertainty
self.psf = psf
def __str__(self):
data = str(self.data)
unit = f" {self.unit}" if self.unit is not None else ""
return data + unit
def __repr__(self):
prefix = self.__class__.__name__ + "("
data = np.array2string(self.data, separator=", ", prefix=prefix)
unit = f", unit='{self.unit}'" if self.unit is not None else ""
return "".join((prefix, data, unit, ")"))
@property
def data(self):
"""
`~numpy.ndarray`-like : The stored dataset.
"""
return self._data
@property
def mask(self):
"""
any type : Mask for the dataset, if any.
Masks should follow the ``numpy`` convention that valid data points are
marked by ``False`` and invalid ones with ``True``.
"""
return self._mask
@mask.setter
def mask(self, value):
self._mask = value
@property
def unit(self):
"""
`~astropy.units.Unit` : Unit for the dataset, if any.
"""
return self._unit
@property
def wcs(self):
"""
any type : A world coordinate system (WCS) for the dataset, if any.
"""
return self._wcs
@wcs.setter
def wcs(self, wcs):
if self._wcs is not None and wcs is not None:
raise ValueError(
"You can only set the wcs attribute with a WCS if no WCS is present."
)
if wcs is None or isinstance(wcs, BaseHighLevelWCS):
self._wcs = wcs
elif isinstance(wcs, BaseLowLevelWCS):
self._wcs = HighLevelWCSWrapper(wcs)
else:
raise TypeError(
"The wcs argument must implement either the high or low level WCS API."
)
@property
def psf(self):
return self._psf
@psf.setter
def psf(self, value):
self._psf = value
@property
def uncertainty(self):
"""
any type : Uncertainty in the dataset, if any.
Should have an attribute ``uncertainty_type`` that defines what kind of
uncertainty is stored, such as ``'std'`` for standard deviation or
``'var'`` for variance. A metaclass defining such an interface is
`~astropy.nddata.NDUncertainty` but isn't mandatory.
"""
return self._uncertainty
@uncertainty.setter
def uncertainty(self, value):
if value is not None:
# There is one requirements on the uncertainty: That
# it has an attribute 'uncertainty_type'.
# If it does not match this requirement convert it to an unknown
# uncertainty.
if not hasattr(value, "uncertainty_type"):
log.info("uncertainty should have attribute uncertainty_type.")
value = UnknownUncertainty(value, copy=False)
# If it is a subclass of NDUncertainty we must set the
# parent_nddata attribute. (#4152)
if isinstance(value, NDUncertainty):
# In case the uncertainty already has a parent create a new
# instance because we need to assume that we don't want to
# steal the uncertainty from another NDData object
if value._parent_nddata is not None:
value = value.__class__(value, copy=False)
# Then link it to this NDData instance (internally this needs
# to be saved as weakref but that's done by NDUncertainty
# setter).
value.parent_nddata = self
self._uncertainty = value