numpy.compress — NumPy v1.11 Manual (original) (raw)

numpy.compress(condition, a, axis=None, out=None)[source]¶

Return selected slices of an array along given axis.

When working along a given axis, a slice along that axis is returned in_output_ for each index where condition evaluates to True. When working on a 1-D array, compress is equivalent to extract.

Parameters:	condition : 1-D array of bools Array that selects which entries to return. If len(condition) is less than the size of a along the given axis, then output is truncated to the length of the condition array. a : array_like Array from which to extract a part. axis : int, optional Axis along which to take slices. If None (default), work on the flattened array. out : ndarray, optional Output array. Its type is preserved and it must be of the right shape to hold the output.
Returns:	compressed_array : ndarray A copy of a without the slices along axis for which _condition_is false.

Parameters:

condition : 1-D array of bools Array that selects which entries to return. If len(condition) is less than the size of a along the given axis, then output is truncated to the length of the condition array. a : array_like Array from which to extract a part. axis : int, optional Axis along which to take slices. If None (default), work on the flattened array. out : ndarray, optional Output array. Its type is preserved and it must be of the right shape to hold the output.

Returns:

compressed_array : ndarray A copy of a without the slices along axis for which _condition_is false.

Examples

a = np.array([[1, 2], [3, 4], [5, 6]]) a array([[1, 2], [3, 4], [5, 6]]) np.compress([0, 1], a, axis=0) array([[3, 4]]) np.compress([False, True, True], a, axis=0) array([[3, 4], [5, 6]]) np.compress([False, True], a, axis=1) array([[2], [4], [6]])

Working on the flattened array does not return slices along an axis but selects elements.

np.compress([False, True], a) array([2])