numpy.ma.MaskedArray.compress

method

ma.MaskedArray. compress ( condition, axis=None, out=None ) [source]

Return a where condition is True.

If condition is a MaskedArray, missing values are considered as False.

Parameters

condition var

Boolean 1-d array selecting which entries to return. If len(condition) is less than the size of a along the axis, then output is truncated to length of condition array.

axis {None, int}, optional

Axis along which the operation must be performed.

out {None, ndarray}, optional

Alternative output array in which to place the result. It must have the same shape as the expected output but the type will be cast if necessary.

Returns

result MaskedArray

A MaskedArray object.

Notes

Please note the difference with compressed ! The output of compress has a mask, the output of compressed does not.

Examples

>>> x = np.ma.array([[1,2,3],[4,5,6],[7,8,9]], mask=[0] + [1,0]*4)
>>> x
masked_array(
  data=[[1, --, 3],
        [--, 5, --],
        [7, --, 9]],
  mask=[[False,  True, False],
        [ True, False,  True],
        [False,  True, False]],
  fill_value=999999)
>>> x.compress([1, 0, 1])
masked_array(data=[1, 3],
             mask=[False, False],
       fill_value=999999)

>>> x.compress([1, 0, 1], axis=1)
masked_array(
  data=[[1, 3],
        [--, --],
        [7, 9]],
  mask=[[False, False],
        [ True,  True],
        [False, False]],
  fill_value=999999)