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scipy.ndimage.

# minimum_filter1d

scipy.ndimage.minimum_filter1d(input, size, axis=-1, output=None, mode='reflect', cval=0.0, origin=0)

  Calculate a 1-D minimum filter along the given axis.

  The lines of the array along the given axis are filtered with a minimum filter of given size.

  Parameters:
    input array_like

      The input array.

    size int

      length along which to calculate 1D minimum

    axis int, optional

      The axis of input along which to calculate. Default is -1.

    output array or dtype, optional

      The array in which to place the output, or the dtype of the returned array. By default an array of the same dtype as input will be created.

    mode{‘reflect’, ‘constant’, ‘nearest’, ‘mirror’, ‘wrap’}, optional

      The mode parameter determines how the input array is extended beyond its boundaries. Default is ‘reflect’. Behavior for each valid value is as follows:

      ‘reflect’ (d c b a | a b c d | d c b a)

        The input is extended by reflecting about the edge of the last pixel. This mode is also sometimes referred to as half-sample symmetric.

      ‘constant’ (k k k k | a b c d | k k k k)

        The input is extended by filling all values beyond the edge with the same constant value, defined by the cval parameter.

      ‘nearest’ (a a a a | a b c d | d d d d)

        The input is extended by replicating the last pixel.

      ‘mirror’ (d c b | a b c d | c b a)

        The input is extended by reflecting about the center of the last pixel. This mode is also sometimes referred to as whole-sample symmetric.

      ‘wrap’ (a b c d | a b c d | a b c d)

        The input is extended by wrapping around to the opposite edge.

      For consistency with the interpolation functions, the following mode names can also be used:

      ‘grid-mirror’

        This is a synonym for ‘reflect’.

      ‘grid-constant’

        This is a synonym for ‘constant’.

      ‘grid-wrap’

        This is a synonym for ‘wrap’.

    cval scalar, optional

      Value to fill past edges of input if mode is ‘constant’. Default is 0.0.

    origin int, optional

      Controls the placement of the filter on the input array’s pixels. A value of 0 (the default) centers the filter over the pixel, with positive values shifting the filter to the left, and negative ones to the right.

  Returns:
    result ndarray.

      Filtered image. Has the same shape as input.

  Notes

  This function implements the MINLIST algorithm [1], as described by Richard Harter [2], and has a guaranteed O(n) performance, n being the input length, regardless of filter size.

  Array API Standard Support

  `minimum_filter1d` has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable `SCIPY_ARRAY_API=1` and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

  Library | CPU | GPU
  --- | --- | ---
  NumPy | ✅ | n/a
  CuPy | n/a | ✅
  PyTorch | ✅ | ⛔
  JAX | ⚠️ no JIT | ⛔
  Dask | ⚠️ computes graph | n/a

  > See Support for the array API standard for more information.

  References

  [1]

  http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.42.2777

  [2]

  http://www.richardhartersworld.com/cri/2001/slidingmin.html

  Examples

      >>> from scipy.ndimage import minimum_filter1d
      >>> minimum_filter1d([2, 8, 0, 4, 1, 9, 9, 0], size=3)
      array([2, 0, 0, 0, 1, 1, 0, 0])