Signature Description
enum class quantile_policy : unsigned char {
 lower_value = 1, // Take the higher index
 higher_value = 2, // Take the lower index
 mid_point = 3, // Average the two quantiles
 linear = 4, // Linearly combine the two quantiles
};
This policy determines how to calculate quantiles when they fall between two values.
Linear is calculates as:
X1 + (X2 – X1) * (1.0 – QT)