Equal-frequency binning divides ordered observations into intervals containing approximately the same number of observations. It is generally preferred for multivariate outlier detection, where rare combinations matter more than isolated univariate extremes. section 9.6
Unlike equal-width binning, equal-frequency binning reduces the distortion caused by extreme values spanning a wide numeric range. The binning method and the chosen number of bins still affect which observations appear rare. section 9.6 section 9.8
Choosing a bin count
Uniform data with values 3.0 and 100.0 demonstrates how bin choices can hide or expose unusual values; PyOD provides get_optimal_n_bins as a bin-count utility. section 9.6
