numpy.extract — NumPy v1.13 Manual (original) (raw)
numpy. extract(condition, arr)[source]¶
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 : ndarray Rank 1 array of values from arr where condition is True. |
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]], dtype=bool) np.extract(condition, arr) array([0, 3, 6, 9])
If condition is boolean:
arr[condition] array([0, 3, 6, 9])