# qml.math.where¶

where(condition, x, y)[source]

Returns elements chosen from x or y depending on a boolean tensor condition.

The input tensors condition, x, and y must all be broadcastable to the same shape.

Parameters
• condition (tensor_like[bool]) – A boolean tensor. Where True, elements from x will be chosen, otherwise y.

• x (tensor_like) – values from which to choose if the condition evaluates to True

• y (tensor_like) – values from which to choose if the condition evaluates to False

Returns

A tensor with elements from x where the condition is True, and y otherwise. The output tensor has the same shape as the input tensors.

Return type

tensor_like

Example

>>> a = torch.tensor([0.6, 0.23, 0.7, 1.5, 1.7], requires_grad=True)
>>> b = torch.tensor([-1., -2., -3., -4., -5.], requires_grad=True)
>>> math.where(a < 1, a, b)
tensor([ 0.6000,  0.2300,  0.7000, -4.0000, -5.0000], grad_fn=<SWhereBackward>)