Reverse piecewise linear sigmoid function

reverse_piecewise_linear_sigmoid.py.py

import numpy as np

def reverse_piecewise_linear_sigmoid(self, x, upper, lower):
    '''
    Reverse piecewise linear sigmoid function to filter a value between two thresholds in a vectorised manner according to:
    
    if x <= lower:
        y = 1
    else:
        y = (upper-x)/(upper-lower)
    if x > upper:
        y = 0
    
    1 ----------
                \
                 \
                  \
                   \
                    \
    0                ----------
    
    Parameters
    ----------
    x : float
        Value to be filtered
    upper : float
        Upper bound of the sigmoid
    lower : float
        Lower bound of the sigmoid

    Returns
    -------
    y : float
        Filtered value
    
    '''
    y = np.maximum(np.minimum((upper-x)/(upper-lower), 1.0), 0.0)
    return y