Module « scipy.ndimage »

Fonction variance - module scipy.ndimage

Signature de la fonction variance

def variance(input, labels=None, index=None) 

Description

variance.__doc__

    Calculate the variance of the values of an N-D image array, optionally at
    specified sub-regions.

    Parameters
    ----------
    input : array_like
        Nd-image data to process.
    labels : array_like, optional
        Labels defining sub-regions in `input`.
        If not None, must be same shape as `input`.
    index : int or sequence of ints, optional
        `labels` to include in output.  If None (default), all values where
        `labels` is non-zero are used.

    Returns
    -------
    variance : float or ndarray
        Values of variance, for each sub-region if `labels` and `index` are
        specified.

    See Also
    --------
    label, standard_deviation, maximum, minimum, extrema

    Examples
    --------
    >>> a = np.array([[1, 2, 0, 0],
    ...               [5, 3, 0, 4],
    ...               [0, 0, 0, 7],
    ...               [9, 3, 0, 0]])
    >>> from scipy import ndimage
    >>> ndimage.variance(a)
    7.609375

    Features to process can be specified using `labels` and `index`:

    >>> lbl, nlbl = ndimage.label(a)
    >>> ndimage.variance(a, lbl, index=np.arange(1, nlbl+1))
    array([ 2.1875,  2.25  ,  9.    ])

    If no index is given, all non-zero `labels` are processed:

    >>> ndimage.variance(a, lbl)
    6.1875