ZHANG, Ruda August 07, 2020:  Correct math: use 1 with set subscript for characteristic function / indicator function of the set; use "[ x ]" instead of "[x]" to avoid GFM checkbox syntax. [1ac98ba]
ZHANG, Ruda October 25, 2019:  Notes on machine learning. [6e74cb4]
ZHANG, Ruda December 30, 2018:  Use dollar style math markup. [1b7036c]
ZHANG, Ruda September 30, 2018:  CSS redesign; more edits. [dd44d96]
ZHANG, Ruda July 16, 2018:  More on density estimation, classification. [4e45e08]
ZHANG, Ruda October 14, 2017:  Merge computational and statistical learning. [a493a55]