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Diffstat (limited to 'numpy/core/multiarray.py')
| -rw-r--r-- | numpy/core/multiarray.py | 315 |
1 files changed, 315 insertions, 0 deletions
diff --git a/numpy/core/multiarray.py b/numpy/core/multiarray.py index 673328397..aafda476f 100644 --- a/numpy/core/multiarray.py +++ b/numpy/core/multiarray.py @@ -7,6 +7,7 @@ by importing from the extension module. """ from . import _multiarray_umath +from .overrides import array_function_dispatch from numpy.core._multiarray_umath import * from numpy.core._multiarray_umath import ( _fastCopyAndTranspose, _flagdict, _insert, _reconstruct, _vec_string, @@ -35,3 +36,317 @@ __all__ = [ 'tracemalloc_domain', 'typeinfo', 'unpackbits', 'unravel_index', 'vdot', 'where', 'zeros'] + +def _empty_like_dispatcher(prototype, dtype=None, order=None, subok=None): + return (prototype,) + + +@array_function_dispatch(_empty_like_dispatcher) +def empty_like(prototype, dtype=None, order='K', subok=True): + """Return a new array with the same shape and type as a given array. + + Parameters + ---------- + prototype : array_like + The shape and data-type of `prototype` define these same attributes + of the returned array. + dtype : data-type, optional + Overrides the data type of the result. + + .. versionadded:: 1.6.0 + order : {'C', 'F', 'A', or 'K'}, optional + Overrides the memory layout of the result. 'C' means C-order, + 'F' means F-order, 'A' means 'F' if ``prototype`` is Fortran + contiguous, 'C' otherwise. 'K' means match the layout of ``prototype`` + as closely as possible. + + .. versionadded:: 1.6.0 + subok : bool, optional. + If True, then the newly created array will use the sub-class + type of 'a', otherwise it will be a base-class array. Defaults + to True. + + Returns + ------- + out : ndarray + Array of uninitialized (arbitrary) data with the same + shape and type as `prototype`. + + See Also + -------- + ones_like : Return an array of ones with shape and type of input. + zeros_like : Return an array of zeros with shape and type of input. + full_like : Return a new array with shape of input filled with value. + empty : Return a new uninitialized array. + + Notes + ----- + This function does *not* initialize the returned array; to do that use + `zeros_like` or `ones_like` instead. It may be marginally faster than + the functions that do set the array values. + + Examples + -------- + >>> a = ([1,2,3], [4,5,6]) # a is array-like + >>> np.empty_like(a) + array([[-1073741821, -1073741821, 3], #random + [ 0, 0, -1073741821]]) + >>> a = np.array([[1., 2., 3.],[4.,5.,6.]]) + >>> np.empty_like(a) + array([[ -2.00000715e+000, 1.48219694e-323, -2.00000572e+000],#random + [ 4.38791518e-305, -2.00000715e+000, 4.17269252e-309]]) + + """ + return _multiarray_umath.empty_like(prototype, dtype, order, subok) + + +def _concatenate_dispatcher(arrays, axis=None, out=None): + for array in arrays: + yield array + yield out + + +@array_function_dispatch(_concatenate_dispatcher) +def concatenate(arrays, axis=0, out=None): + """ + concatenate((a1, a2, ...), axis=0, out=None) + + Join a sequence of arrays along an existing axis. + + Parameters + ---------- + a1, a2, ... : sequence of array_like + The arrays must have the same shape, except in the dimension + corresponding to `axis` (the first, by default). + axis : int, optional + The axis along which the arrays will be joined. If axis is None, + arrays are flattened before use. Default is 0. + out : ndarray, optional + If provided, the destination to place the result. The shape must be + correct, matching that of what concatenate would have returned if no + out argument were specified. + + Returns + ------- + res : ndarray + The concatenated array. + + See Also + -------- + ma.concatenate : Concatenate function that preserves input masks. + array_split : Split an array into multiple sub-arrays of equal or + near-equal size. + split : Split array into a list of multiple sub-arrays of equal size. + 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). + stack : Stack 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) + block : Assemble arrays from blocks. + + Notes + ----- + When one or more of the arrays to be concatenated is a MaskedArray, + this function will return a MaskedArray object instead of an ndarray, + but the input masks are *not* preserved. In cases where a MaskedArray + is expected as input, use the ma.concatenate function from the masked + array module instead. + + Examples + -------- + >>> a = np.array([[1, 2], [3, 4]]) + >>> b = np.array([[5, 6]]) + >>> np.concatenate((a, b), axis=0) + array([[1, 2], + [3, 4], + [5, 6]]) + >>> np.concatenate((a, b.T), axis=1) + array([[1, 2, 5], + [3, 4, 6]]) + >>> np.concatenate((a, b), axis=None) + array([1, 2, 3, 4, 5, 6]) + + This function will not preserve masking of MaskedArray inputs. + + >>> a = np.ma.arange(3) + >>> a[1] = np.ma.masked + >>> b = np.arange(2, 5) + >>> a + masked_array(data=[0, --, 2], + mask=[False, True, False], + fill_value=999999) + >>> b + array([2, 3, 4]) + >>> np.concatenate([a, b]) + masked_array(data=[0, 1, 2, 2, 3, 4], + mask=False, + fill_value=999999) + >>> np.ma.concatenate([a, b]) + masked_array(data=[0, --, 2, 2, 3, 4], + mask=[False, True, False, False, False, False], + fill_value=999999) + + """ + return _multiarray_umath.concatenate(arrays, axis, out) + + +def _inner_dispatcher(a, b): + return (a, b) + + +@array_function_dispatch(_inner_dispatcher) +def inner(a, b): + """ + Inner product of two arrays. + + Ordinary inner product of vectors for 1-D arrays (without complex + conjugation), in higher dimensions a sum product over the last axes. + + Parameters + ---------- + a, b : array_like + If `a` and `b` are nonscalar, their last dimensions must match. + + Returns + ------- + out : ndarray + `out.shape = a.shape[:-1] + b.shape[:-1]` + + Raises + ------ + ValueError + If the last dimension of `a` and `b` has different size. + + See Also + -------- + tensordot : Sum products over arbitrary axes. + dot : Generalised matrix product, using second last dimension of `b`. + einsum : Einstein summation convention. + + Notes + ----- + For vectors (1-D arrays) it computes the ordinary inner-product:: + + np.inner(a, b) = sum(a[:]*b[:]) + + More generally, if `ndim(a) = r > 0` and `ndim(b) = s > 0`:: + + np.inner(a, b) = np.tensordot(a, b, axes=(-1,-1)) + + or explicitly:: + + np.inner(a, b)[i0,...,ir-1,j0,...,js-1] + = sum(a[i0,...,ir-1,:]*b[j0,...,js-1,:]) + + In addition `a` or `b` may be scalars, in which case:: + + np.inner(a,b) = a*b + + Examples + -------- + Ordinary inner product for vectors: + + >>> a = np.array([1,2,3]) + >>> b = np.array([0,1,0]) + >>> np.inner(a, b) + 2 + + A multidimensional example: + + >>> a = np.arange(24).reshape((2,3,4)) + >>> b = np.arange(4) + >>> np.inner(a, b) + array([[ 14, 38, 62], + [ 86, 110, 134]]) + + An example where `b` is a scalar: + + >>> np.inner(np.eye(2), 7) + array([[ 7., 0.], + [ 0., 7.]]) + + """ + return _multiarray_umath.inner(a, b) + + +def _where_dispatcher(condition, x, y): + return (condition, x, y) + + +@array_function_dispatch(_where_dispatcher) +def where(condition, x, y): + """ + where(condition, [x, y]) + + Return elements chosen from `x` or `y` depending on `condition`. + + .. note:: + When only `condition` is provided, this function is a shorthand for + ``np.asarray(condition).nonzero()``. Using `nonzero` directly should be + preferred, as it behaves correctly for subclasses. The rest of this + documentation covers only the case where all three arguments are + provided. + + Parameters + ---------- + condition : array_like, bool + Where True, yield `x`, otherwise yield `y`. + x, y : array_like + Values from which to choose. `x`, `y` and `condition` need to be + broadcastable to some shape. + + Returns + ------- + out : ndarray + An array with elements from `x` where `condition` is True, and elements + from `y` elsewhere. + + See Also + -------- + choose + nonzero : The function that is called when x and y are omitted + + Notes + ----- + If all the arrays are 1-D, `where` is equivalent to:: + + [xv if c else yv + for c, xv, yv in zip(condition, x, y)] + + Examples + -------- + >>> a = np.arange(10) + >>> a + array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) + >>> np.where(a < 5, a, 10*a) + array([ 0, 1, 2, 3, 4, 50, 60, 70, 80, 90]) + + This can be used on multidimensional arrays too: + + >>> np.where([[True, False], [True, True]], + ... [[1, 2], [3, 4]], + ... [[9, 8], [7, 6]]) + array([[1, 8], + [3, 4]]) + + The shapes of x, y, and the condition are broadcast together: + + >>> x, y = np.ogrid[:3, :4] + >>> np.where(x < y, x, 10 + y) # both x and 10+y are broadcast + array([[10, 0, 0, 0], + [10, 11, 1, 1], + [10, 11, 12, 2]]) + + >>> a = np.array([[0, 1, 2], + ... [0, 2, 4], + ... [0, 3, 6]]) + >>> np.where(a < 4, a, -1) # -1 is broadcast + array([[ 0, 1, 2], + [ 0, 2, -1], + [ 0, 3, -1]]) + """ + # _multiarray_umath.where only accepts positional arguments + args = tuple(a for a in (x, y) if a is not None) + return _multiarray_umath.where(condition, *args) |