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1245 lines
37 KiB
Python
1245 lines
37 KiB
Python
from __future__ import division, absolute_import, print_function
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import functools
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import warnings
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import numpy.core.numeric as _nx
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from numpy.core.numeric import (
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asarray, zeros, outer, concatenate, array, asanyarray
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)
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from numpy.core.fromnumeric import reshape, transpose
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from numpy.core.multiarray import normalize_axis_index
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from numpy.core import overrides
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from numpy.core import vstack, atleast_3d
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from numpy.core.shape_base import _arrays_for_stack_dispatcher
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from numpy.lib.index_tricks import ndindex
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from numpy.matrixlib.defmatrix import matrix # this raises all the right alarm bells
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__all__ = [
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'column_stack', 'row_stack', 'dstack', 'array_split', 'split',
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'hsplit', 'vsplit', 'dsplit', 'apply_over_axes', 'expand_dims',
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'apply_along_axis', 'kron', 'tile', 'get_array_wrap', 'take_along_axis',
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'put_along_axis'
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]
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array_function_dispatch = functools.partial(
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overrides.array_function_dispatch, module='numpy')
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def _make_along_axis_idx(arr_shape, indices, axis):
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# compute dimensions to iterate over
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if not _nx.issubdtype(indices.dtype, _nx.integer):
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raise IndexError('`indices` must be an integer array')
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if len(arr_shape) != indices.ndim:
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raise ValueError(
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"`indices` and `arr` must have the same number of dimensions")
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shape_ones = (1,) * indices.ndim
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dest_dims = list(range(axis)) + [None] + list(range(axis+1, indices.ndim))
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# build a fancy index, consisting of orthogonal aranges, with the
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# requested index inserted at the right location
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fancy_index = []
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for dim, n in zip(dest_dims, arr_shape):
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if dim is None:
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fancy_index.append(indices)
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else:
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ind_shape = shape_ones[:dim] + (-1,) + shape_ones[dim+1:]
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fancy_index.append(_nx.arange(n).reshape(ind_shape))
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return tuple(fancy_index)
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def _take_along_axis_dispatcher(arr, indices, axis):
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return (arr, indices)
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@array_function_dispatch(_take_along_axis_dispatcher)
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def take_along_axis(arr, indices, axis):
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"""
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Take values from the input array by matching 1d index and data slices.
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This iterates over matching 1d slices oriented along the specified axis in
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the index and data arrays, and uses the former to look up values in the
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latter. These slices can be different lengths.
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Functions returning an index along an axis, like `argsort` and
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`argpartition`, produce suitable indices for this function.
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.. versionadded:: 1.15.0
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Parameters
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----------
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arr: ndarray (Ni..., M, Nk...)
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Source array
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indices: ndarray (Ni..., J, Nk...)
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Indices to take along each 1d slice of `arr`. This must match the
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dimension of arr, but dimensions Ni and Nj only need to broadcast
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against `arr`.
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axis: int
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The axis to take 1d slices along. If axis is None, the input array is
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treated as if it had first been flattened to 1d, for consistency with
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`sort` and `argsort`.
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Returns
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-------
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out: ndarray (Ni..., J, Nk...)
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The indexed result.
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Notes
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-----
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This is equivalent to (but faster than) the following use of `ndindex` and
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`s_`, which sets each of ``ii`` and ``kk`` to a tuple of indices::
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Ni, M, Nk = a.shape[:axis], a.shape[axis], a.shape[axis+1:]
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J = indices.shape[axis] # Need not equal M
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out = np.empty(Ni + (J,) + Nk)
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for ii in ndindex(Ni):
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for kk in ndindex(Nk):
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a_1d = a [ii + s_[:,] + kk]
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indices_1d = indices[ii + s_[:,] + kk]
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out_1d = out [ii + s_[:,] + kk]
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for j in range(J):
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out_1d[j] = a_1d[indices_1d[j]]
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Equivalently, eliminating the inner loop, the last two lines would be::
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out_1d[:] = a_1d[indices_1d]
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See Also
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--------
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take : Take along an axis, using the same indices for every 1d slice
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put_along_axis :
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Put values into the destination array by matching 1d index and data slices
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Examples
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--------
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For this sample array
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>>> a = np.array([[10, 30, 20], [60, 40, 50]])
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We can sort either by using sort directly, or argsort and this function
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>>> np.sort(a, axis=1)
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array([[10, 20, 30],
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[40, 50, 60]])
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>>> ai = np.argsort(a, axis=1); ai
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array([[0, 2, 1],
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[1, 2, 0]])
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>>> np.take_along_axis(a, ai, axis=1)
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array([[10, 20, 30],
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[40, 50, 60]])
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The same works for max and min, if you expand the dimensions:
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>>> np.expand_dims(np.max(a, axis=1), axis=1)
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array([[30],
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[60]])
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>>> ai = np.expand_dims(np.argmax(a, axis=1), axis=1)
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>>> ai
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array([[1],
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[0]])
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>>> np.take_along_axis(a, ai, axis=1)
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array([[30],
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[60]])
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If we want to get the max and min at the same time, we can stack the
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indices first
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>>> ai_min = np.expand_dims(np.argmin(a, axis=1), axis=1)
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>>> ai_max = np.expand_dims(np.argmax(a, axis=1), axis=1)
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>>> ai = np.concatenate([ai_min, ai_max], axis=1)
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>>> ai
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array([[0, 1],
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[1, 0]])
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>>> np.take_along_axis(a, ai, axis=1)
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array([[10, 30],
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[40, 60]])
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"""
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# normalize inputs
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if axis is None:
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arr = arr.flat
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arr_shape = (len(arr),) # flatiter has no .shape
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axis = 0
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else:
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axis = normalize_axis_index(axis, arr.ndim)
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arr_shape = arr.shape
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# use the fancy index
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return arr[_make_along_axis_idx(arr_shape, indices, axis)]
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def _put_along_axis_dispatcher(arr, indices, values, axis):
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return (arr, indices, values)
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@array_function_dispatch(_put_along_axis_dispatcher)
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def put_along_axis(arr, indices, values, axis):
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"""
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Put values into the destination array by matching 1d index and data slices.
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This iterates over matching 1d slices oriented along the specified axis in
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the index and data arrays, and uses the former to place values into the
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latter. These slices can be different lengths.
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Functions returning an index along an axis, like `argsort` and
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`argpartition`, produce suitable indices for this function.
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.. versionadded:: 1.15.0
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Parameters
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----------
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arr: ndarray (Ni..., M, Nk...)
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Destination array.
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indices: ndarray (Ni..., J, Nk...)
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Indices to change along each 1d slice of `arr`. This must match the
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dimension of arr, but dimensions in Ni and Nj may be 1 to broadcast
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against `arr`.
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values: array_like (Ni..., J, Nk...)
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values to insert at those indices. Its shape and dimension are
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broadcast to match that of `indices`.
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axis: int
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The axis to take 1d slices along. If axis is None, the destination
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array is treated as if a flattened 1d view had been created of it.
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Notes
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-----
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This is equivalent to (but faster than) the following use of `ndindex` and
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`s_`, which sets each of ``ii`` and ``kk`` to a tuple of indices::
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Ni, M, Nk = a.shape[:axis], a.shape[axis], a.shape[axis+1:]
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J = indices.shape[axis] # Need not equal M
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for ii in ndindex(Ni):
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for kk in ndindex(Nk):
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a_1d = a [ii + s_[:,] + kk]
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indices_1d = indices[ii + s_[:,] + kk]
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values_1d = values [ii + s_[:,] + kk]
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for j in range(J):
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a_1d[indices_1d[j]] = values_1d[j]
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Equivalently, eliminating the inner loop, the last two lines would be::
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a_1d[indices_1d] = values_1d
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See Also
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--------
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take_along_axis :
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Take values from the input array by matching 1d index and data slices
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Examples
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--------
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For this sample array
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>>> a = np.array([[10, 30, 20], [60, 40, 50]])
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We can replace the maximum values with:
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>>> ai = np.expand_dims(np.argmax(a, axis=1), axis=1)
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>>> ai
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array([[1],
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[0]])
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>>> np.put_along_axis(a, ai, 99, axis=1)
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>>> a
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array([[10, 99, 20],
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[99, 40, 50]])
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"""
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# normalize inputs
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if axis is None:
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arr = arr.flat
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axis = 0
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arr_shape = (len(arr),) # flatiter has no .shape
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else:
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axis = normalize_axis_index(axis, arr.ndim)
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arr_shape = arr.shape
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# use the fancy index
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arr[_make_along_axis_idx(arr_shape, indices, axis)] = values
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def _apply_along_axis_dispatcher(func1d, axis, arr, *args, **kwargs):
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return (arr,)
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@array_function_dispatch(_apply_along_axis_dispatcher)
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def apply_along_axis(func1d, axis, arr, *args, **kwargs):
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"""
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Apply a function to 1-D slices along the given axis.
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Execute `func1d(a, *args)` where `func1d` operates on 1-D arrays and `a`
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is a 1-D slice of `arr` along `axis`.
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This is equivalent to (but faster than) the following use of `ndindex` and
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`s_`, which sets each of ``ii``, ``jj``, and ``kk`` to a tuple of indices::
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Ni, Nk = a.shape[:axis], a.shape[axis+1:]
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for ii in ndindex(Ni):
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for kk in ndindex(Nk):
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f = func1d(arr[ii + s_[:,] + kk])
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Nj = f.shape
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for jj in ndindex(Nj):
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out[ii + jj + kk] = f[jj]
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Equivalently, eliminating the inner loop, this can be expressed as::
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Ni, Nk = a.shape[:axis], a.shape[axis+1:]
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for ii in ndindex(Ni):
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for kk in ndindex(Nk):
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out[ii + s_[...,] + kk] = func1d(arr[ii + s_[:,] + kk])
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Parameters
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----------
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func1d : function (M,) -> (Nj...)
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This function should accept 1-D arrays. It is applied to 1-D
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slices of `arr` along the specified axis.
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axis : integer
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Axis along which `arr` is sliced.
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arr : ndarray (Ni..., M, Nk...)
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Input array.
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args : any
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Additional arguments to `func1d`.
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kwargs : any
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Additional named arguments to `func1d`.
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.. versionadded:: 1.9.0
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Returns
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-------
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out : ndarray (Ni..., Nj..., Nk...)
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The output array. The shape of `out` is identical to the shape of
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`arr`, except along the `axis` dimension. This axis is removed, and
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replaced with new dimensions equal to the shape of the return value
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of `func1d`. So if `func1d` returns a scalar `out` will have one
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fewer dimensions than `arr`.
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See Also
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--------
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apply_over_axes : Apply a function repeatedly over multiple axes.
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Examples
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--------
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>>> def my_func(a):
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... \"\"\"Average first and last element of a 1-D array\"\"\"
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... return (a[0] + a[-1]) * 0.5
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>>> b = np.array([[1,2,3], [4,5,6], [7,8,9]])
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>>> np.apply_along_axis(my_func, 0, b)
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array([4., 5., 6.])
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>>> np.apply_along_axis(my_func, 1, b)
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array([2., 5., 8.])
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For a function that returns a 1D array, the number of dimensions in
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`outarr` is the same as `arr`.
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>>> b = np.array([[8,1,7], [4,3,9], [5,2,6]])
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>>> np.apply_along_axis(sorted, 1, b)
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array([[1, 7, 8],
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[3, 4, 9],
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[2, 5, 6]])
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For a function that returns a higher dimensional array, those dimensions
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are inserted in place of the `axis` dimension.
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>>> b = np.array([[1,2,3], [4,5,6], [7,8,9]])
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>>> np.apply_along_axis(np.diag, -1, b)
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array([[[1, 0, 0],
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[0, 2, 0],
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[0, 0, 3]],
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[[4, 0, 0],
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[0, 5, 0],
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[0, 0, 6]],
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[[7, 0, 0],
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[0, 8, 0],
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[0, 0, 9]]])
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"""
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# handle negative axes
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arr = asanyarray(arr)
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nd = arr.ndim
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axis = normalize_axis_index(axis, nd)
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# arr, with the iteration axis at the end
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in_dims = list(range(nd))
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inarr_view = transpose(arr, in_dims[:axis] + in_dims[axis+1:] + [axis])
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# compute indices for the iteration axes, and append a trailing ellipsis to
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# prevent 0d arrays decaying to scalars, which fixes gh-8642
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inds = ndindex(inarr_view.shape[:-1])
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inds = (ind + (Ellipsis,) for ind in inds)
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# invoke the function on the first item
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try:
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ind0 = next(inds)
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except StopIteration:
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raise ValueError('Cannot apply_along_axis when any iteration dimensions are 0')
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res = asanyarray(func1d(inarr_view[ind0], *args, **kwargs))
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# build a buffer for storing evaluations of func1d.
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# remove the requested axis, and add the new ones on the end.
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# laid out so that each write is contiguous.
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# for a tuple index inds, buff[inds] = func1d(inarr_view[inds])
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buff = zeros(inarr_view.shape[:-1] + res.shape, res.dtype)
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# permutation of axes such that out = buff.transpose(buff_permute)
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buff_dims = list(range(buff.ndim))
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buff_permute = (
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buff_dims[0 : axis] +
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buff_dims[buff.ndim-res.ndim : buff.ndim] +
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buff_dims[axis : buff.ndim-res.ndim]
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)
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# matrices have a nasty __array_prepare__ and __array_wrap__
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if not isinstance(res, matrix):
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buff = res.__array_prepare__(buff)
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# save the first result, then compute and save all remaining results
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buff[ind0] = res
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for ind in inds:
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buff[ind] = asanyarray(func1d(inarr_view[ind], *args, **kwargs))
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if not isinstance(res, matrix):
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# wrap the array, to preserve subclasses
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buff = res.__array_wrap__(buff)
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# finally, rotate the inserted axes back to where they belong
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return transpose(buff, buff_permute)
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else:
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# matrices have to be transposed first, because they collapse dimensions!
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out_arr = transpose(buff, buff_permute)
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return res.__array_wrap__(out_arr)
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def _apply_over_axes_dispatcher(func, a, axes):
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return (a,)
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|
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|
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@array_function_dispatch(_apply_over_axes_dispatcher)
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def apply_over_axes(func, a, axes):
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"""
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Apply a function repeatedly over multiple axes.
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`func` is called as `res = func(a, axis)`, where `axis` is the first
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element of `axes`. The result `res` of the function call must have
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either the same dimensions as `a` or one less dimension. If `res`
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has one less dimension than `a`, a dimension is inserted before
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`axis`. The call to `func` is then repeated for each axis in `axes`,
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with `res` as the first argument.
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Parameters
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----------
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func : function
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This function must take two arguments, `func(a, axis)`.
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a : array_like
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Input array.
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axes : array_like
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Axes over which `func` is applied; the elements must be integers.
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Returns
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-------
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apply_over_axis : ndarray
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The output array. The number of dimensions is the same as `a`,
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but the shape can be different. This depends on whether `func`
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changes the shape of its output with respect to its input.
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|
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See Also
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--------
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apply_along_axis :
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Apply a function to 1-D slices of an array along the given axis.
|
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|
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Notes
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------
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This function is equivalent to tuple axis arguments to reorderable ufuncs
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with keepdims=True. Tuple axis arguments to ufuncs have been available since
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version 1.7.0.
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Examples
|
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--------
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>>> a = np.arange(24).reshape(2,3,4)
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>>> a
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array([[[ 0, 1, 2, 3],
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[ 4, 5, 6, 7],
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[ 8, 9, 10, 11]],
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[[12, 13, 14, 15],
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[16, 17, 18, 19],
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[20, 21, 22, 23]]])
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Sum over axes 0 and 2. The result has same number of dimensions
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as the original array:
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>>> np.apply_over_axes(np.sum, a, [0,2])
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array([[[ 60],
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[ 92],
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[124]]])
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Tuple axis arguments to ufuncs are equivalent:
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>>> np.sum(a, axis=(0,2), keepdims=True)
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array([[[ 60],
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[ 92],
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[124]]])
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"""
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val = asarray(a)
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N = a.ndim
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if array(axes).ndim == 0:
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axes = (axes,)
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for axis in axes:
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if axis < 0:
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axis = N + axis
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args = (val, axis)
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res = func(*args)
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if res.ndim == val.ndim:
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val = res
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else:
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res = expand_dims(res, axis)
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if res.ndim == val.ndim:
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val = res
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else:
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raise ValueError("function is not returning "
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"an array of the correct shape")
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|
return val
|
|
|
|
|
|
def _expand_dims_dispatcher(a, axis):
|
|
return (a,)
|
|
|
|
|
|
@array_function_dispatch(_expand_dims_dispatcher)
|
|
def expand_dims(a, axis):
|
|
"""
|
|
Expand the shape of an array.
|
|
|
|
Insert a new axis that will appear at the `axis` position in the expanded
|
|
array shape.
|
|
|
|
.. note:: Previous to NumPy 1.13.0, neither ``axis < -a.ndim - 1`` nor
|
|
``axis > a.ndim`` raised errors or put the new axis where documented.
|
|
Those axis values are now deprecated and will raise an AxisError in the
|
|
future.
|
|
|
|
Parameters
|
|
----------
|
|
a : array_like
|
|
Input array.
|
|
axis : int
|
|
Position in the expanded axes where the new axis is placed.
|
|
|
|
Returns
|
|
-------
|
|
res : ndarray
|
|
View of `a` with the number of dimensions increased by one.
|
|
|
|
See Also
|
|
--------
|
|
squeeze : The inverse operation, removing singleton dimensions
|
|
reshape : Insert, remove, and combine dimensions, and resize existing ones
|
|
doc.indexing, atleast_1d, atleast_2d, atleast_3d
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.array([1,2])
|
|
>>> x.shape
|
|
(2,)
|
|
|
|
The following is equivalent to ``x[np.newaxis,:]`` or ``x[np.newaxis]``:
|
|
|
|
>>> y = np.expand_dims(x, axis=0)
|
|
>>> y
|
|
array([[1, 2]])
|
|
>>> y.shape
|
|
(1, 2)
|
|
|
|
>>> y = np.expand_dims(x, axis=1) # Equivalent to x[:,np.newaxis]
|
|
>>> y
|
|
array([[1],
|
|
[2]])
|
|
>>> y.shape
|
|
(2, 1)
|
|
|
|
Note that some examples may use ``None`` instead of ``np.newaxis``. These
|
|
are the same objects:
|
|
|
|
>>> np.newaxis is None
|
|
True
|
|
|
|
"""
|
|
if isinstance(a, matrix):
|
|
a = asarray(a)
|
|
else:
|
|
a = asanyarray(a)
|
|
|
|
shape = a.shape
|
|
if axis > a.ndim or axis < -a.ndim - 1:
|
|
# 2017-05-17, 1.13.0
|
|
warnings.warn("Both axis > a.ndim and axis < -a.ndim - 1 are "
|
|
"deprecated and will raise an AxisError in the future.",
|
|
DeprecationWarning, stacklevel=3)
|
|
# When the deprecation period expires, delete this if block,
|
|
if axis < 0:
|
|
axis = axis + a.ndim + 1
|
|
# and uncomment the following line.
|
|
# axis = normalize_axis_index(axis, a.ndim + 1)
|
|
return a.reshape(shape[:axis] + (1,) + shape[axis:])
|
|
|
|
|
|
row_stack = vstack
|
|
|
|
|
|
def _column_stack_dispatcher(tup):
|
|
return _arrays_for_stack_dispatcher(tup)
|
|
|
|
|
|
@array_function_dispatch(_column_stack_dispatcher)
|
|
def column_stack(tup):
|
|
"""
|
|
Stack 1-D arrays as columns into a 2-D array.
|
|
|
|
Take a sequence of 1-D arrays and stack them as columns
|
|
to make a single 2-D array. 2-D arrays are stacked as-is,
|
|
just like with `hstack`. 1-D arrays are turned into 2-D columns
|
|
first.
|
|
|
|
Parameters
|
|
----------
|
|
tup : sequence of 1-D or 2-D arrays.
|
|
Arrays to stack. All of them must have the same first dimension.
|
|
|
|
Returns
|
|
-------
|
|
stacked : 2-D array
|
|
The array formed by stacking the given arrays.
|
|
|
|
See Also
|
|
--------
|
|
stack, hstack, vstack, concatenate
|
|
|
|
Examples
|
|
--------
|
|
>>> a = np.array((1,2,3))
|
|
>>> b = np.array((2,3,4))
|
|
>>> np.column_stack((a,b))
|
|
array([[1, 2],
|
|
[2, 3],
|
|
[3, 4]])
|
|
|
|
"""
|
|
if not overrides.ARRAY_FUNCTION_ENABLED:
|
|
# raise warning if necessary
|
|
_arrays_for_stack_dispatcher(tup, stacklevel=2)
|
|
|
|
arrays = []
|
|
for v in tup:
|
|
arr = array(v, copy=False, subok=True)
|
|
if arr.ndim < 2:
|
|
arr = array(arr, copy=False, subok=True, ndmin=2).T
|
|
arrays.append(arr)
|
|
return _nx.concatenate(arrays, 1)
|
|
|
|
|
|
def _dstack_dispatcher(tup):
|
|
return _arrays_for_stack_dispatcher(tup)
|
|
|
|
|
|
@array_function_dispatch(_dstack_dispatcher)
|
|
def dstack(tup):
|
|
"""
|
|
Stack arrays in sequence depth wise (along third axis).
|
|
|
|
This is equivalent to concatenation along the third axis after 2-D arrays
|
|
of shape `(M,N)` have been reshaped to `(M,N,1)` and 1-D arrays of shape
|
|
`(N,)` have been reshaped to `(1,N,1)`. Rebuilds arrays divided by
|
|
`dsplit`.
|
|
|
|
This function makes most sense for arrays with up to 3 dimensions. For
|
|
instance, for pixel-data with a height (first axis), width (second axis),
|
|
and r/g/b channels (third axis). The functions `concatenate`, `stack` and
|
|
`block` provide more general stacking and concatenation operations.
|
|
|
|
Parameters
|
|
----------
|
|
tup : sequence of arrays
|
|
The arrays must have the same shape along all but the third axis.
|
|
1-D or 2-D arrays must have the same shape.
|
|
|
|
Returns
|
|
-------
|
|
stacked : ndarray
|
|
The array formed by stacking the given arrays, will be at least 3-D.
|
|
|
|
See Also
|
|
--------
|
|
stack : Join a sequence of arrays along a new axis.
|
|
vstack : Stack along first axis.
|
|
hstack : Stack along second axis.
|
|
concatenate : Join a sequence of arrays along an existing axis.
|
|
dsplit : Split array along third axis.
|
|
|
|
Examples
|
|
--------
|
|
>>> a = np.array((1,2,3))
|
|
>>> b = np.array((2,3,4))
|
|
>>> np.dstack((a,b))
|
|
array([[[1, 2],
|
|
[2, 3],
|
|
[3, 4]]])
|
|
|
|
>>> a = np.array([[1],[2],[3]])
|
|
>>> b = np.array([[2],[3],[4]])
|
|
>>> np.dstack((a,b))
|
|
array([[[1, 2]],
|
|
[[2, 3]],
|
|
[[3, 4]]])
|
|
|
|
"""
|
|
if not overrides.ARRAY_FUNCTION_ENABLED:
|
|
# raise warning if necessary
|
|
_arrays_for_stack_dispatcher(tup, stacklevel=2)
|
|
|
|
arrs = atleast_3d(*tup)
|
|
if not isinstance(arrs, list):
|
|
arrs = [arrs]
|
|
return _nx.concatenate(arrs, 2)
|
|
|
|
|
|
def _replace_zero_by_x_arrays(sub_arys):
|
|
for i in range(len(sub_arys)):
|
|
if _nx.ndim(sub_arys[i]) == 0:
|
|
sub_arys[i] = _nx.empty(0, dtype=sub_arys[i].dtype)
|
|
elif _nx.sometrue(_nx.equal(_nx.shape(sub_arys[i]), 0)):
|
|
sub_arys[i] = _nx.empty(0, dtype=sub_arys[i].dtype)
|
|
return sub_arys
|
|
|
|
|
|
def _array_split_dispatcher(ary, indices_or_sections, axis=None):
|
|
return (ary, indices_or_sections)
|
|
|
|
|
|
@array_function_dispatch(_array_split_dispatcher)
|
|
def array_split(ary, indices_or_sections, axis=0):
|
|
"""
|
|
Split an array into multiple sub-arrays.
|
|
|
|
Please refer to the ``split`` documentation. The only difference
|
|
between these functions is that ``array_split`` allows
|
|
`indices_or_sections` to be an integer that does *not* equally
|
|
divide the axis. For an array of length l that should be split
|
|
into n sections, it returns l % n sub-arrays of size l//n + 1
|
|
and the rest of size l//n.
|
|
|
|
See Also
|
|
--------
|
|
split : Split array into multiple sub-arrays of equal size.
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.arange(8.0)
|
|
>>> np.array_split(x, 3)
|
|
[array([0., 1., 2.]), array([3., 4., 5.]), array([6., 7.])]
|
|
|
|
>>> x = np.arange(7.0)
|
|
>>> np.array_split(x, 3)
|
|
[array([0., 1., 2.]), array([3., 4.]), array([5., 6.])]
|
|
|
|
"""
|
|
try:
|
|
Ntotal = ary.shape[axis]
|
|
except AttributeError:
|
|
Ntotal = len(ary)
|
|
try:
|
|
# handle array case.
|
|
Nsections = len(indices_or_sections) + 1
|
|
div_points = [0] + list(indices_or_sections) + [Ntotal]
|
|
except TypeError:
|
|
# indices_or_sections is a scalar, not an array.
|
|
Nsections = int(indices_or_sections)
|
|
if Nsections <= 0:
|
|
raise ValueError('number sections must be larger than 0.')
|
|
Neach_section, extras = divmod(Ntotal, Nsections)
|
|
section_sizes = ([0] +
|
|
extras * [Neach_section+1] +
|
|
(Nsections-extras) * [Neach_section])
|
|
div_points = _nx.array(section_sizes, dtype=_nx.intp).cumsum()
|
|
|
|
sub_arys = []
|
|
sary = _nx.swapaxes(ary, axis, 0)
|
|
for i in range(Nsections):
|
|
st = div_points[i]
|
|
end = div_points[i + 1]
|
|
sub_arys.append(_nx.swapaxes(sary[st:end], axis, 0))
|
|
|
|
return sub_arys
|
|
|
|
|
|
def _split_dispatcher(ary, indices_or_sections, axis=None):
|
|
return (ary, indices_or_sections)
|
|
|
|
|
|
@array_function_dispatch(_split_dispatcher)
|
|
def split(ary, indices_or_sections, axis=0):
|
|
"""
|
|
Split an array into multiple sub-arrays.
|
|
|
|
Parameters
|
|
----------
|
|
ary : ndarray
|
|
Array to be divided into sub-arrays.
|
|
indices_or_sections : int or 1-D array
|
|
If `indices_or_sections` is an integer, N, the array will be divided
|
|
into N equal arrays along `axis`. If such a split is not possible,
|
|
an error is raised.
|
|
|
|
If `indices_or_sections` is a 1-D array of sorted integers, the entries
|
|
indicate where along `axis` the array is split. For example,
|
|
``[2, 3]`` would, for ``axis=0``, result in
|
|
|
|
- ary[:2]
|
|
- ary[2:3]
|
|
- ary[3:]
|
|
|
|
If an index exceeds the dimension of the array along `axis`,
|
|
an empty sub-array is returned correspondingly.
|
|
axis : int, optional
|
|
The axis along which to split, default is 0.
|
|
|
|
Returns
|
|
-------
|
|
sub-arrays : list of ndarrays
|
|
A list of sub-arrays.
|
|
|
|
Raises
|
|
------
|
|
ValueError
|
|
If `indices_or_sections` is given as an integer, but
|
|
a split does not result in equal division.
|
|
|
|
See Also
|
|
--------
|
|
array_split : Split an array into multiple sub-arrays of equal or
|
|
near-equal size. Does not raise an exception if
|
|
an equal division cannot be made.
|
|
hsplit : Split array into multiple sub-arrays horizontally (column-wise).
|
|
vsplit : Split array into multiple sub-arrays vertically (row wise).
|
|
dsplit : Split array into multiple sub-arrays along the 3rd axis (depth).
|
|
concatenate : Join a sequence of arrays along an existing axis.
|
|
stack : Join a sequence of arrays along a new axis.
|
|
hstack : Stack arrays in sequence horizontally (column wise).
|
|
vstack : Stack arrays in sequence vertically (row wise).
|
|
dstack : Stack arrays in sequence depth wise (along third dimension).
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.arange(9.0)
|
|
>>> np.split(x, 3)
|
|
[array([0., 1., 2.]), array([3., 4., 5.]), array([6., 7., 8.])]
|
|
|
|
>>> x = np.arange(8.0)
|
|
>>> np.split(x, [3, 5, 6, 10])
|
|
[array([0., 1., 2.]),
|
|
array([3., 4.]),
|
|
array([5.]),
|
|
array([6., 7.]),
|
|
array([], dtype=float64)]
|
|
|
|
"""
|
|
try:
|
|
len(indices_or_sections)
|
|
except TypeError:
|
|
sections = indices_or_sections
|
|
N = ary.shape[axis]
|
|
if N % sections:
|
|
raise ValueError(
|
|
'array split does not result in an equal division')
|
|
res = array_split(ary, indices_or_sections, axis)
|
|
return res
|
|
|
|
|
|
def _hvdsplit_dispatcher(ary, indices_or_sections):
|
|
return (ary, indices_or_sections)
|
|
|
|
|
|
@array_function_dispatch(_hvdsplit_dispatcher)
|
|
def hsplit(ary, indices_or_sections):
|
|
"""
|
|
Split an array into multiple sub-arrays horizontally (column-wise).
|
|
|
|
Please refer to the `split` documentation. `hsplit` is equivalent
|
|
to `split` with ``axis=1``, the array is always split along the second
|
|
axis regardless of the array dimension.
|
|
|
|
See Also
|
|
--------
|
|
split : Split an array into multiple sub-arrays of equal size.
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.arange(16.0).reshape(4, 4)
|
|
>>> x
|
|
array([[ 0., 1., 2., 3.],
|
|
[ 4., 5., 6., 7.],
|
|
[ 8., 9., 10., 11.],
|
|
[12., 13., 14., 15.]])
|
|
>>> np.hsplit(x, 2)
|
|
[array([[ 0., 1.],
|
|
[ 4., 5.],
|
|
[ 8., 9.],
|
|
[12., 13.]]),
|
|
array([[ 2., 3.],
|
|
[ 6., 7.],
|
|
[10., 11.],
|
|
[14., 15.]])]
|
|
>>> np.hsplit(x, np.array([3, 6]))
|
|
[array([[ 0., 1., 2.],
|
|
[ 4., 5., 6.],
|
|
[ 8., 9., 10.],
|
|
[12., 13., 14.]]),
|
|
array([[ 3.],
|
|
[ 7.],
|
|
[11.],
|
|
[15.]]),
|
|
array([], shape=(4, 0), dtype=float64)]
|
|
|
|
With a higher dimensional array the split is still along the second axis.
|
|
|
|
>>> x = np.arange(8.0).reshape(2, 2, 2)
|
|
>>> x
|
|
array([[[0., 1.],
|
|
[2., 3.]],
|
|
[[4., 5.],
|
|
[6., 7.]]])
|
|
>>> np.hsplit(x, 2)
|
|
[array([[[0., 1.]],
|
|
[[4., 5.]]]),
|
|
array([[[2., 3.]],
|
|
[[6., 7.]]])]
|
|
|
|
"""
|
|
if _nx.ndim(ary) == 0:
|
|
raise ValueError('hsplit only works on arrays of 1 or more dimensions')
|
|
if ary.ndim > 1:
|
|
return split(ary, indices_or_sections, 1)
|
|
else:
|
|
return split(ary, indices_or_sections, 0)
|
|
|
|
|
|
@array_function_dispatch(_hvdsplit_dispatcher)
|
|
def vsplit(ary, indices_or_sections):
|
|
"""
|
|
Split an array into multiple sub-arrays vertically (row-wise).
|
|
|
|
Please refer to the ``split`` documentation. ``vsplit`` is equivalent
|
|
to ``split`` with `axis=0` (default), the array is always split along the
|
|
first axis regardless of the array dimension.
|
|
|
|
See Also
|
|
--------
|
|
split : Split an array into multiple sub-arrays of equal size.
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.arange(16.0).reshape(4, 4)
|
|
>>> x
|
|
array([[ 0., 1., 2., 3.],
|
|
[ 4., 5., 6., 7.],
|
|
[ 8., 9., 10., 11.],
|
|
[12., 13., 14., 15.]])
|
|
>>> np.vsplit(x, 2)
|
|
[array([[0., 1., 2., 3.],
|
|
[4., 5., 6., 7.]]), array([[ 8., 9., 10., 11.],
|
|
[12., 13., 14., 15.]])]
|
|
>>> np.vsplit(x, np.array([3, 6]))
|
|
[array([[ 0., 1., 2., 3.],
|
|
[ 4., 5., 6., 7.],
|
|
[ 8., 9., 10., 11.]]), array([[12., 13., 14., 15.]]), array([], shape=(0, 4), dtype=float64)]
|
|
|
|
With a higher dimensional array the split is still along the first axis.
|
|
|
|
>>> x = np.arange(8.0).reshape(2, 2, 2)
|
|
>>> x
|
|
array([[[0., 1.],
|
|
[2., 3.]],
|
|
[[4., 5.],
|
|
[6., 7.]]])
|
|
>>> np.vsplit(x, 2)
|
|
[array([[[0., 1.],
|
|
[2., 3.]]]), array([[[4., 5.],
|
|
[6., 7.]]])]
|
|
|
|
"""
|
|
if _nx.ndim(ary) < 2:
|
|
raise ValueError('vsplit only works on arrays of 2 or more dimensions')
|
|
return split(ary, indices_or_sections, 0)
|
|
|
|
|
|
@array_function_dispatch(_hvdsplit_dispatcher)
|
|
def dsplit(ary, indices_or_sections):
|
|
"""
|
|
Split array into multiple sub-arrays along the 3rd axis (depth).
|
|
|
|
Please refer to the `split` documentation. `dsplit` is equivalent
|
|
to `split` with ``axis=2``, the array is always split along the third
|
|
axis provided the array dimension is greater than or equal to 3.
|
|
|
|
See Also
|
|
--------
|
|
split : Split an array into multiple sub-arrays of equal size.
|
|
|
|
Examples
|
|
--------
|
|
>>> x = np.arange(16.0).reshape(2, 2, 4)
|
|
>>> x
|
|
array([[[ 0., 1., 2., 3.],
|
|
[ 4., 5., 6., 7.]],
|
|
[[ 8., 9., 10., 11.],
|
|
[12., 13., 14., 15.]]])
|
|
>>> np.dsplit(x, 2)
|
|
[array([[[ 0., 1.],
|
|
[ 4., 5.]],
|
|
[[ 8., 9.],
|
|
[12., 13.]]]), array([[[ 2., 3.],
|
|
[ 6., 7.]],
|
|
[[10., 11.],
|
|
[14., 15.]]])]
|
|
>>> np.dsplit(x, np.array([3, 6]))
|
|
[array([[[ 0., 1., 2.],
|
|
[ 4., 5., 6.]],
|
|
[[ 8., 9., 10.],
|
|
[12., 13., 14.]]]),
|
|
array([[[ 3.],
|
|
[ 7.]],
|
|
[[11.],
|
|
[15.]]]),
|
|
array([], shape=(2, 2, 0), dtype=float64)]
|
|
"""
|
|
if _nx.ndim(ary) < 3:
|
|
raise ValueError('dsplit only works on arrays of 3 or more dimensions')
|
|
return split(ary, indices_or_sections, 2)
|
|
|
|
def get_array_prepare(*args):
|
|
"""Find the wrapper for the array with the highest priority.
|
|
|
|
In case of ties, leftmost wins. If no wrapper is found, return None
|
|
"""
|
|
wrappers = sorted((getattr(x, '__array_priority__', 0), -i,
|
|
x.__array_prepare__) for i, x in enumerate(args)
|
|
if hasattr(x, '__array_prepare__'))
|
|
if wrappers:
|
|
return wrappers[-1][-1]
|
|
return None
|
|
|
|
def get_array_wrap(*args):
|
|
"""Find the wrapper for the array with the highest priority.
|
|
|
|
In case of ties, leftmost wins. If no wrapper is found, return None
|
|
"""
|
|
wrappers = sorted((getattr(x, '__array_priority__', 0), -i,
|
|
x.__array_wrap__) for i, x in enumerate(args)
|
|
if hasattr(x, '__array_wrap__'))
|
|
if wrappers:
|
|
return wrappers[-1][-1]
|
|
return None
|
|
|
|
|
|
def _kron_dispatcher(a, b):
|
|
return (a, b)
|
|
|
|
|
|
@array_function_dispatch(_kron_dispatcher)
|
|
def kron(a, b):
|
|
"""
|
|
Kronecker product of two arrays.
|
|
|
|
Computes the Kronecker product, a composite array made of blocks of the
|
|
second array scaled by the first.
|
|
|
|
Parameters
|
|
----------
|
|
a, b : array_like
|
|
|
|
Returns
|
|
-------
|
|
out : ndarray
|
|
|
|
See Also
|
|
--------
|
|
outer : The outer product
|
|
|
|
Notes
|
|
-----
|
|
The function assumes that the number of dimensions of `a` and `b`
|
|
are the same, if necessary prepending the smallest with ones.
|
|
If `a.shape = (r0,r1,..,rN)` and `b.shape = (s0,s1,...,sN)`,
|
|
the Kronecker product has shape `(r0*s0, r1*s1, ..., rN*SN)`.
|
|
The elements are products of elements from `a` and `b`, organized
|
|
explicitly by::
|
|
|
|
kron(a,b)[k0,k1,...,kN] = a[i0,i1,...,iN] * b[j0,j1,...,jN]
|
|
|
|
where::
|
|
|
|
kt = it * st + jt, t = 0,...,N
|
|
|
|
In the common 2-D case (N=1), the block structure can be visualized::
|
|
|
|
[[ a[0,0]*b, a[0,1]*b, ... , a[0,-1]*b ],
|
|
[ ... ... ],
|
|
[ a[-1,0]*b, a[-1,1]*b, ... , a[-1,-1]*b ]]
|
|
|
|
|
|
Examples
|
|
--------
|
|
>>> np.kron([1,10,100], [5,6,7])
|
|
array([ 5, 6, 7, ..., 500, 600, 700])
|
|
>>> np.kron([5,6,7], [1,10,100])
|
|
array([ 5, 50, 500, ..., 7, 70, 700])
|
|
|
|
>>> np.kron(np.eye(2), np.ones((2,2)))
|
|
array([[1., 1., 0., 0.],
|
|
[1., 1., 0., 0.],
|
|
[0., 0., 1., 1.],
|
|
[0., 0., 1., 1.]])
|
|
|
|
>>> a = np.arange(100).reshape((2,5,2,5))
|
|
>>> b = np.arange(24).reshape((2,3,4))
|
|
>>> c = np.kron(a,b)
|
|
>>> c.shape
|
|
(2, 10, 6, 20)
|
|
>>> I = (1,3,0,2)
|
|
>>> J = (0,2,1)
|
|
>>> J1 = (0,) + J # extend to ndim=4
|
|
>>> S1 = (1,) + b.shape
|
|
>>> K = tuple(np.array(I) * np.array(S1) + np.array(J1))
|
|
>>> c[K] == a[I]*b[J]
|
|
True
|
|
|
|
"""
|
|
b = asanyarray(b)
|
|
a = array(a, copy=False, subok=True, ndmin=b.ndim)
|
|
ndb, nda = b.ndim, a.ndim
|
|
if (nda == 0 or ndb == 0):
|
|
return _nx.multiply(a, b)
|
|
as_ = a.shape
|
|
bs = b.shape
|
|
if not a.flags.contiguous:
|
|
a = reshape(a, as_)
|
|
if not b.flags.contiguous:
|
|
b = reshape(b, bs)
|
|
nd = ndb
|
|
if (ndb != nda):
|
|
if (ndb > nda):
|
|
as_ = (1,)*(ndb-nda) + as_
|
|
else:
|
|
bs = (1,)*(nda-ndb) + bs
|
|
nd = nda
|
|
result = outer(a, b).reshape(as_+bs)
|
|
axis = nd-1
|
|
for _ in range(nd):
|
|
result = concatenate(result, axis=axis)
|
|
wrapper = get_array_prepare(a, b)
|
|
if wrapper is not None:
|
|
result = wrapper(result)
|
|
wrapper = get_array_wrap(a, b)
|
|
if wrapper is not None:
|
|
result = wrapper(result)
|
|
return result
|
|
|
|
|
|
def _tile_dispatcher(A, reps):
|
|
return (A, reps)
|
|
|
|
|
|
@array_function_dispatch(_tile_dispatcher)
|
|
def tile(A, reps):
|
|
"""
|
|
Construct an array by repeating A the number of times given by reps.
|
|
|
|
If `reps` has length ``d``, the result will have dimension of
|
|
``max(d, A.ndim)``.
|
|
|
|
If ``A.ndim < d``, `A` is promoted to be d-dimensional by prepending new
|
|
axes. So a shape (3,) array is promoted to (1, 3) for 2-D replication,
|
|
or shape (1, 1, 3) for 3-D replication. If this is not the desired
|
|
behavior, promote `A` to d-dimensions manually before calling this
|
|
function.
|
|
|
|
If ``A.ndim > d``, `reps` is promoted to `A`.ndim by pre-pending 1's to it.
|
|
Thus for an `A` of shape (2, 3, 4, 5), a `reps` of (2, 2) is treated as
|
|
(1, 1, 2, 2).
|
|
|
|
Note : Although tile may be used for broadcasting, it is strongly
|
|
recommended to use numpy's broadcasting operations and functions.
|
|
|
|
Parameters
|
|
----------
|
|
A : array_like
|
|
The input array.
|
|
reps : array_like
|
|
The number of repetitions of `A` along each axis.
|
|
|
|
Returns
|
|
-------
|
|
c : ndarray
|
|
The tiled output array.
|
|
|
|
See Also
|
|
--------
|
|
repeat : Repeat elements of an array.
|
|
broadcast_to : Broadcast an array to a new shape
|
|
|
|
Examples
|
|
--------
|
|
>>> a = np.array([0, 1, 2])
|
|
>>> np.tile(a, 2)
|
|
array([0, 1, 2, 0, 1, 2])
|
|
>>> np.tile(a, (2, 2))
|
|
array([[0, 1, 2, 0, 1, 2],
|
|
[0, 1, 2, 0, 1, 2]])
|
|
>>> np.tile(a, (2, 1, 2))
|
|
array([[[0, 1, 2, 0, 1, 2]],
|
|
[[0, 1, 2, 0, 1, 2]]])
|
|
|
|
>>> b = np.array([[1, 2], [3, 4]])
|
|
>>> np.tile(b, 2)
|
|
array([[1, 2, 1, 2],
|
|
[3, 4, 3, 4]])
|
|
>>> np.tile(b, (2, 1))
|
|
array([[1, 2],
|
|
[3, 4],
|
|
[1, 2],
|
|
[3, 4]])
|
|
|
|
>>> c = np.array([1,2,3,4])
|
|
>>> np.tile(c,(4,1))
|
|
array([[1, 2, 3, 4],
|
|
[1, 2, 3, 4],
|
|
[1, 2, 3, 4],
|
|
[1, 2, 3, 4]])
|
|
"""
|
|
try:
|
|
tup = tuple(reps)
|
|
except TypeError:
|
|
tup = (reps,)
|
|
d = len(tup)
|
|
if all(x == 1 for x in tup) and isinstance(A, _nx.ndarray):
|
|
# Fixes the problem that the function does not make a copy if A is a
|
|
# numpy array and the repetitions are 1 in all dimensions
|
|
return _nx.array(A, copy=True, subok=True, ndmin=d)
|
|
else:
|
|
# Note that no copy of zero-sized arrays is made. However since they
|
|
# have no data there is no risk of an inadvertent overwrite.
|
|
c = _nx.array(A, copy=False, subok=True, ndmin=d)
|
|
if (d < c.ndim):
|
|
tup = (1,)*(c.ndim-d) + tup
|
|
shape_out = tuple(s*t for s, t in zip(c.shape, tup))
|
|
n = c.size
|
|
if n > 0:
|
|
for dim_in, nrep in zip(c.shape, tup):
|
|
if nrep != 1:
|
|
c = c.reshape(-1, n).repeat(nrep, 0)
|
|
n //= dim_in
|
|
return c.reshape(shape_out)
|