Source code for pyinterpolate.semivariogram.theoretical.spatial_dependency_index

from typing import Tuple




def calculate_spatial_dependence_index(nugget: float, sill: float) -> Tuple:
    """
    Function estimates spatial dependence index and its ratio.

    Parameters
    ----------
    nugget : float
        Semivariogram nugget.

    sill : float
        Partial sill, difference between total sill and nugget. If given,
        then partial sill is fixed to this value.

    Returns
    -------
    : Tuple[float, str]
        ratio, descriptive spatial dependency strength

    Raises
    ------
    ValueError
        Nugget is equal to zero.

    References
    ----------
    [1] CAMBARDELLA, C.A.; MOORMAN, T.B.; PARKIN, T.B.; KARLEN, D.L.; NOVAK,
    J.M.; TURCO, R.F.; KONOPKA, A.E. Field-scale variability of soil
    properties in central Iowa soils.
    Soil Science Society of America Journal, v. 58, n. 5, p. 1501-1511, 1994.

    Examples
    --------
    >>> from pyinterpolate import calculate_spatial_dependence_index
    >>>
    >>>
    >>> ratio_percent, strength = calculate_spatial_dependence_index(
    ...     nugget=0.1,
    ...     sill=0.9
    ... )
    >>> print((ratio_percent, strength))
    (10.0, 'strong')
    """

    if nugget == 0:
        raise ValueError('Nugget cannot be set to 0 to '
                         'calculate spatial dependence index')

    total_sill = sill + nugget

    ratio = (nugget / total_sill) * 100

    if ratio < 25:
        spatial_dependency = 'strong'
    elif ratio < 75:
        spatial_dependency = 'moderate'
    elif ratio < 95:
        spatial_dependency = 'weak'
    else:
        spatial_dependency = 'no spatial dependence'

    return ratio, spatial_dependency