mxnet.np.extract

extract(condition, arr)

Return the elements of an array that satisfy some condition.

This is equivalent to np.compress(ravel(condition), ravel(arr)). If condition is boolean np.extract is equivalent to arr[condition].

Note that place does the exact opposite of extract.

Parameters

  • condition (array_like) – An array whose nonzero or True entries indicate the elements of arr to extract.

  • arr (array_like) – Input array of the same size as condition.

Returns

extract – Rank 1 array of values from arr where condition is True.

Return type

ndarray

See also

take(), put(), copyto(), compress(), place()

Examples

>>> arr = np.arange(12).reshape((3, 4))
>>> arr
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11]])
>>> condition = np.mod(arr, 3)==0
>>> condition
array([[ True, False, False,  True],
       [False, False,  True, False],
       [False,  True, False, False]])
>>> np.extract(condition, arr)
array([0, 3, 6, 9])

If condition is boolean:

>>> arr[condition]
array([0, 3, 6, 9])