# Source code for mars.tensor.base.expand_dims

#!/usr/bin/env python
# -*- coding: utf-8 -*-
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# Licensed under the Apache License, Version 2.0 (the "License");
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# http://www.apache.org/licenses/LICENSE-2.0
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import numpy as np
from ..datasource import tensor as astensor
[docs]def expand_dims(a, axis):
"""
Expand the shape of a tensor.
Insert a new axis that will appear at the `axis` position in the expanded
array shape.
Parameters
----------
a : array_like
Input tensor.
axis : int
Position in the expanded axes where the new axis is placed.
Returns
-------
res : Tensor
Output tensor. The number of dimensions is one greater than that of
the input tensor.
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
--------
>>> import mars.tensor as mt
>>> x = mt.array([1,2])
>>> x.shape
(2,)
The following is equivalent to ``x[mt.newaxis,:]`` or ``x[mt.newaxis]``:
>>> y = mt.expand_dims(x, axis=0)
>>> y.execute()
array([[1, 2]])
>>> y.shape
(1, 2)
>>> y = mt.expand_dims(x, axis=1) # Equivalent to x[:,mt.newaxis]
>>> y.execute()
array([[1],
[2]])
>>> y.shape
(2, 1)
Note that some examples may use ``None`` instead of ``np.newaxis``. These
are the same objects:
>>> mt.newaxis is None
True
"""
a = astensor(a)
if axis > a.ndim or axis < -a.ndim - 1:
raise np.AxisError(
f"Axis must be between -{a.ndim + 1} and {a.ndim}, got {axis}"
)
axis = axis if axis >= 0 else axis + a.ndim + 1
indexes = (slice(None),) * axis + (np.newaxis,) + (slice(None),) * (a.ndim - axis)
return a[indexes]