qfeval_functions.functions.ffill

ffill(x, dim=-1)[source]

Forward fill missing values along the specified dimension.

This function propagates the last valid (non-NaN) values forward along the specified dimension. For each NaN value, it is replaced with the most recent valid value that appears before it along the dimension. If no valid value exists before a NaN, it remains NaN.

Parameters:

x (Tensor) – The input tensor containing values to be filled. May contain NaN values that will be replaced.
dim (int) – The dimension along which to perform forward fill. Default is -1 (the last dimension).

Returns:

A tensor of the same shape as the input, with NaN values replaced by the nearest preceding valid values where possible.

Return type:

Tensor

Example

>>> # Simple 1D forward fill
>>> x = torch.tensor([1.0, nan, nan, 4.0, 5.0])
>>> QF.ffill(x)
tensor([1., 1., 1., 4., 5.])

>>> # 2D example with dim=1
>>> x = torch.tensor([[nan, 2.0, nan, 4.0],
...                   [5.0, nan, nan, 8.0]])
>>> QF.ffill(x, dim=1)
tensor([[nan, 2., 2., 4.],
        [5., 5., 5., 8.]])

>>> # Forward fill along columns (dim=0)
>>> x = torch.tensor([[1.0, nan, 3.0],
...                   [nan, 2.0, nan],
...                   [4.0, nan, nan]])
>>> QF.ffill(x, dim=0)
tensor([[1., nan, 3.],
        [1., 2., 3.],
        [4., 2., 3.]])