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# xarray.dot#

xarray.dot(*arrays, dim=None, **kwargs)[source]#

Generalized dot product for xarray objects. Like np.einsum, but provides a simpler interface based on array dimension names.

Parameters:
• *arrays (DataArray or Variable) β Arrays to compute.

• dim (str, iterable of hashable, "..." or None, optional) β Which dimensions to sum over. Ellipsis (ββ¦β) sums over all dimensions. If not specified, then all the common dimensions are summed over.

• **kwargs (dict) β Additional keyword arguments passed to numpy.einsum or dask.array.einsum

Returns:

DataArray

See also

numpy.einsum, dask.array.einsum, opt_einsum.contract

Notes

We recommend installing the optional opt_einsum package, or alternatively passing optimize=True, which is passed through to np.einsum, and works for most array backends.

Examples

>>> da_a = xr.DataArray(np.arange(3 * 2).reshape(3, 2), dims=["a", "b"])
>>> da_b = xr.DataArray(np.arange(3 * 2 * 2).reshape(3, 2, 2), dims=["a", "b", "c"])
>>> da_c = xr.DataArray(np.arange(2 * 3).reshape(2, 3), dims=["c", "d"])
>>> da_a
<xarray.DataArray (a: 3, b: 2)> Size: 48B
array([[0, 1],
[2, 3],
[4, 5]])
Dimensions without coordinates: a, b
>>> da_b
<xarray.DataArray (a: 3, b: 2, c: 2)> Size: 96B
array([[[ 0,  1],
[ 2,  3]],

[[ 4,  5],
[ 6,  7]],

[[ 8,  9],
[10, 11]]])
Dimensions without coordinates: a, b, c
>>> da_c
<xarray.DataArray (c: 2, d: 3)> Size: 48B
array([[0, 1, 2],
[3, 4, 5]])
Dimensions without coordinates: c, d
>>> xr.dot(da_a, da_b, dim=["a", "b"])
<xarray.DataArray (c: 2)> Size: 16B
array([110, 125])
Dimensions without coordinates: c
>>> xr.dot(da_a, da_b, dim=["a"])
<xarray.DataArray (b: 2, c: 2)> Size: 32B
array([[40, 46],
[70, 79]])
Dimensions without coordinates: b, c
>>> xr.dot(da_a, da_b, da_c, dim=["b", "c"])
<xarray.DataArray (a: 3, d: 3)> Size: 72B
array([[  9,  14,  19],
[ 93, 150, 207],
[273, 446, 619]])
Dimensions without coordinates: a, d
>>> xr.dot(da_a, da_b)
<xarray.DataArray (c: 2)> Size: 16B
array([110, 125])
Dimensions without coordinates: c
>>> xr.dot(da_a, da_b, dim=...)
<xarray.DataArray ()> Size: 8B
array(235)