dask.array.ma.where

dask.array.ma.where

dask.array.ma.where(condition, x=None, y=None)[source]

Return a masked array with elements from x or y, depending on condition.

This docstring was copied from numpy.ma.core.where.

Some inconsistencies with the Dask version may exist.

Note

When only condition is provided, this function is identical to nonzero. The rest of this documentation covers only the case where all three arguments are provided.

Parameters
conditionarray_like, bool

Where True, yield x, otherwise yield y.

x, yarray_like, optional

Values from which to choose. x, y and condition need to be broadcastable to some shape.

Returns
outMaskedArray

An masked array with masked elements where the condition is masked, elements from x where condition is True, and elements from y elsewhere.

See also

numpy.where

Equivalent function in the top-level NumPy module.

nonzero

The function that is called when x and y are omitted

Examples

>>> x = np.ma.array(np.arange(9.).reshape(3, 3), mask=[[0, 1, 0],  
...                                                    [1, 0, 1],
...                                                    [0, 1, 0]])
>>> x  
masked_array(
  data=[[0.0, --, 2.0],
        [--, 4.0, --],
        [6.0, --, 8.0]],
  mask=[[False,  True, False],
        [ True, False,  True],
        [False,  True, False]],
  fill_value=1e+20)
>>> np.ma.where(x > 5, x, -3.1416)  
masked_array(
  data=[[-3.1416, --, -3.1416],
        [--, -3.1416, --],
        [6.0, --, 8.0]],
  mask=[[False,  True, False],
        [ True, False,  True],
        [False,  True, False]],
  fill_value=1e+20)

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