.. currentmodule:: numpy.ma .. for doctests >>> from numpy import ma .. _numpy.ma.constants: Constants of the :mod:`numpy.ma` module ======================================= In addition to the :class:`MaskedArray` class, the :mod:`numpy.ma` module defines several constants. .. data:: masked The :attr:`masked` constant is a special case of :class:`MaskedArray`, with a float datatype and a null shape. It is used to test whether a specific entry of a masked array is masked, or to mask one or several entries of a masked array:: >>> import numpy as np >>> x = ma.array([1, 2, 3], mask=[0, 1, 0]) >>> x[1] is ma.masked True >>> x[-1] = ma.masked >>> x masked_array(data=[1, --, --], mask=[False, True, True], fill_value=999999) .. data:: nomask Value indicating that a masked array has no invalid entry. :attr:`nomask` is used internally to speed up computations when the mask is not needed. It is represented internally as ``np.False_``. .. data:: masked_print_option String used in lieu of missing data when a masked array is printed. By default, this string is ``'--'``. Use ``set_display()`` to change the default string. Example usage: ``numpy.ma.masked_print_option.set_display('X')`` replaces missing data with ``'X'``. .. _maskedarray.baseclass: The :class:`MaskedArray` class ============================== .. class:: MaskedArray A subclass of :class:`~numpy.ndarray` designed to manipulate numerical arrays with missing data. An instance of :class:`MaskedArray` can be thought as the combination of several elements: * The :attr:`~MaskedArray.data`, as a regular :class:`numpy.ndarray` of any shape or datatype (the data). * A boolean :attr:`~numpy.ma.MaskedArray.mask` with the same shape as the data, where a ``True`` value indicates that the corresponding element of the data is invalid. The special value :const:`nomask` is also acceptable for arrays without named fields, and indicates that no data is invalid. * A :attr:`~numpy.ma.MaskedArray.fill_value`, a value that may be used to replace the invalid entries in order to return a standard :class:`numpy.ndarray`. .. _ma-attributes: Attributes and properties of masked arrays ------------------------------------------ .. seealso:: :ref:`Array Attributes ` .. autoattribute:: numpy::ma.MaskedArray.data .. autoattribute:: numpy::ma.MaskedArray.mask .. autoattribute:: numpy::ma.MaskedArray.recordmask .. autoattribute:: numpy::ma.MaskedArray.fill_value .. autoattribute:: numpy::ma.MaskedArray.baseclass .. autoattribute:: numpy::ma.MaskedArray.sharedmask .. autoattribute:: numpy::ma.MaskedArray.hardmask As :class:`MaskedArray` is a subclass of :class:`~numpy.ndarray`, a masked array also inherits all the attributes and properties of a :class:`~numpy.ndarray` instance. .. autosummary:: :toctree: generated/ MaskedArray.base MaskedArray.ctypes MaskedArray.dtype MaskedArray.flags MaskedArray.itemsize MaskedArray.nbytes MaskedArray.ndim MaskedArray.shape MaskedArray.size MaskedArray.strides MaskedArray.imag MaskedArray.real MaskedArray.flat MaskedArray.__array_priority__ :class:`MaskedArray` methods ============================ .. seealso:: :ref:`Array methods ` Conversion ---------- .. autosummary:: :toctree: generated/ MaskedArray.__float__ MaskedArray.__int__ MaskedArray.view MaskedArray.astype MaskedArray.byteswap MaskedArray.compressed MaskedArray.filled MaskedArray.tofile MaskedArray.toflex MaskedArray.tolist MaskedArray.torecords MaskedArray.tostring MaskedArray.tobytes Shape manipulation ------------------ For reshape, resize, and transpose, the single tuple argument may be replaced with ``n`` integers which will be interpreted as an n-tuple. .. autosummary:: :toctree: generated/ MaskedArray.flatten MaskedArray.ravel MaskedArray.reshape MaskedArray.resize MaskedArray.squeeze MaskedArray.swapaxes MaskedArray.transpose MaskedArray.T Item selection and manipulation ------------------------------- For array methods that take an ``axis`` keyword, it defaults to None. If axis is None, then the array is treated as a 1-D array. Any other value for ``axis`` represents the dimension along which the operation should proceed. .. autosummary:: :toctree: generated/ MaskedArray.argmax MaskedArray.argmin MaskedArray.argsort MaskedArray.choose MaskedArray.compress MaskedArray.diagonal MaskedArray.fill MaskedArray.item MaskedArray.nonzero MaskedArray.put MaskedArray.repeat MaskedArray.searchsorted MaskedArray.sort MaskedArray.take Pickling and copy ----------------- .. autosummary:: :toctree: generated/ MaskedArray.copy MaskedArray.dump MaskedArray.dumps Calculations ------------ .. autosummary:: :toctree: generated/ MaskedArray.all MaskedArray.anom MaskedArray.any MaskedArray.clip MaskedArray.conj MaskedArray.conjugate MaskedArray.cumprod MaskedArray.cumsum MaskedArray.max MaskedArray.mean MaskedArray.min MaskedArray.prod MaskedArray.product MaskedArray.ptp MaskedArray.round MaskedArray.std MaskedArray.sum MaskedArray.trace MaskedArray.var Arithmetic and comparison operations ------------------------------------ .. index:: comparison, arithmetic, operation, operator Comparison operators: ~~~~~~~~~~~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.__lt__ MaskedArray.__le__ MaskedArray.__gt__ MaskedArray.__ge__ MaskedArray.__eq__ MaskedArray.__ne__ Truth value of an array (:class:`bool() `): ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.__bool__ Arithmetic: ~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.__abs__ MaskedArray.__add__ MaskedArray.__radd__ MaskedArray.__sub__ MaskedArray.__rsub__ MaskedArray.__mul__ MaskedArray.__rmul__ MaskedArray.__div__ MaskedArray.__truediv__ MaskedArray.__rtruediv__ MaskedArray.__floordiv__ MaskedArray.__rfloordiv__ MaskedArray.__mod__ MaskedArray.__rmod__ MaskedArray.__divmod__ MaskedArray.__rdivmod__ MaskedArray.__pow__ MaskedArray.__rpow__ MaskedArray.__lshift__ MaskedArray.__rlshift__ MaskedArray.__rshift__ MaskedArray.__rrshift__ MaskedArray.__and__ MaskedArray.__rand__ MaskedArray.__or__ MaskedArray.__ror__ MaskedArray.__xor__ MaskedArray.__rxor__ Arithmetic, in-place: ~~~~~~~~~~~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.__iadd__ MaskedArray.__isub__ MaskedArray.__imul__ MaskedArray.__idiv__ MaskedArray.__itruediv__ MaskedArray.__ifloordiv__ MaskedArray.__imod__ MaskedArray.__ipow__ MaskedArray.__ilshift__ MaskedArray.__irshift__ MaskedArray.__iand__ MaskedArray.__ior__ MaskedArray.__ixor__ Representation -------------- .. autosummary:: :toctree: generated/ MaskedArray.__repr__ MaskedArray.__str__ MaskedArray.ids MaskedArray.iscontiguous Special methods --------------- For standard library functions: .. autosummary:: :toctree: generated/ MaskedArray.__copy__ MaskedArray.__deepcopy__ MaskedArray.__getstate__ MaskedArray.__reduce__ MaskedArray.__setstate__ Basic customization: .. autosummary:: :toctree: generated/ MaskedArray.__new__ MaskedArray.__array__ MaskedArray.__array_wrap__ Container customization: (see :ref:`Indexing `) .. autosummary:: :toctree: generated/ MaskedArray.__len__ MaskedArray.__getitem__ MaskedArray.__setitem__ MaskedArray.__delitem__ MaskedArray.__contains__ Specific methods ---------------- Handling the mask ~~~~~~~~~~~~~~~~~ The following methods can be used to access information about the mask or to manipulate the mask. .. autosummary:: :toctree: generated/ MaskedArray.__setmask__ MaskedArray.harden_mask MaskedArray.soften_mask MaskedArray.unshare_mask MaskedArray.shrink_mask Handling the `fill_value` ~~~~~~~~~~~~~~~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.get_fill_value MaskedArray.set_fill_value Counting the missing elements ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. autosummary:: :toctree: generated/ MaskedArray.count