chainer.functions.select_item¶

chainer.functions.select_item(x, t)[source]¶

Select elements stored in given indices.

This function returns t.choose(x.T), that means y[i] == x[i, t[i]] for all i.

Parameters:	x (`Variable` or `numpy.ndarray` or `cupy.ndarray`) – Variable storing arrays. A two-dimensional float array. t (`Variable` or `numpy.ndarray` or `cupy.ndarray`) – Variable storing index numbers. A one-dimensional int array. Length of the `t` should be equal to `x.shape[0]`.
Returns:	Variable that holds `t`-th element of `x`.
Return type:	Variable

Example

>>> x = np.array([[0, 1, 2], [3, 4, 5]], 'f')
>>> t = np.array([0, 2], 'i')
>>> y = F.select_item(x, t)
>>> y.shape
(2,)
>>> y.data
array([ 0.,  5.], dtype=float32)