Source code for pastas.stats.sgi

"""This module contains methods to compute the Standardized Groundwater Index."""

from numpy import linspace
from pandas import Series
from scipy.stats import norm

[docs]def sgi(series: Series) -> Series: """Method to compute the Standardized Groundwater Index :cite:t:`bloomfield_analysis_2013`. Parameters ---------- series: pandas.Series Returns ------- sgi_series: pandas.Series Pandas time series of the groundwater levels. Time series index should be a pandas DatetimeIndex. """ series = series.copy() # Create a copy to ensure series is untouched. # Loop over the months for month in range(1, 13): data = series[series.index.month == month] n = data.size # Number of observations pmin = 1 / (2 * n) pmax = 1 - pmin sgi_values = norm.ppf(linspace(pmin, pmax, n)) series.loc[data.sort_values().index] = sgi_values return series