Skip to main content
`Ctrl`+`K`
scipy.ndimage.

# maximum

scipy.ndimage.maximum(input, labels=None, index=None)

  Calculate the maximum of the values of an array over labeled regions.

  Parameters:
    input array_like

      Array_like of values. For each region specified by labels, the maximal values of input over the region is computed.

    labels array_like, optional

      An array of integers marking different regions over which the maximum value of input is to be computed. labels must have the same shape as input. If labels is not specified, the maximum over the whole array is returned.

    index array_like, optional

      A list of region labels that are taken into account for computing the maxima. If index is None, the maximum over all elements where labels is non-zero is returned.

  Returns:
    output float or list of floats

      List of maxima of input over the regions determined by labels and whose index is in index. If index or labels are not specified, a float is returned: the maximal value of input if labels is None, and the maximal value of elements where labels is greater than zero if index is None.

  See also

  `label`, `minimum`, `median`, `maximum_position`, `extrema`, `sum`, `mean`, `variance`
  `standard_deviation`

  Notes

  The function returns a Python list and not a NumPy array, use np.array to convert the list to an array.

  Examples

      >>> import numpy as np
      >>> a = np.arange(16).reshape((4,4))
      >>> a
      array([[ 0,  1,  2,  3],
             [ 4,  5,  6,  7],
             [ 8,  9, 10, 11],
             [12, 13, 14, 15]])
      >>> labels = np.zeros_like(a)
      >>> labels[:2,:2] = 1
      >>> labels[2:, 1:3] = 2
      >>> labels
      array([[1, 1, 0, 0],
             [1, 1, 0, 0],
             [0, 2, 2, 0],
             [0, 2, 2, 0]])
      >>> from scipy import ndimage
      >>> ndimage.maximum(a)
      15
      >>> ndimage.maximum(a, labels=labels, index=[1,2])
      [5, 14]
      >>> ndimage.maximum(a, labels=labels)
      14

      >>> b = np.array([[1, 2, 0, 0],
      ...               [5, 3, 0, 4],
      ...               [0, 0, 0, 7],
      ...               [9, 3, 0, 0]])
      >>> labels, labels_nb = ndimage.label(b)
      >>> labels
      array([[1, 1, 0, 0],
             [1, 1, 0, 2],
             [0, 0, 0, 2],
             [3, 3, 0, 0]], dtype=int32)
      >>> ndimage.maximum(b, labels=labels, index=np.arange(1, labels_nb + 1))
      [5, 7, 9]