Stochastics are an oscillator and signal line described by George Lane based on each day’s close within the total trading range of past N days. This should not be confused with stochastic processes etc in mathematics, the two are unrelated.
The %K line is the close position within the past N-days trading range (highest high to lowest low) expressed as a percentage 0 to 100.
close - Nday low %K = 100 * -------------------- Nday high - Nday low
An extreme of 0 is reached for a close at the day’s low which is also a new N-day low. Likewise 100 for a close at the day’s high and a new N-day high. A signal line %D is added by smoothing %K with a simple moving average (see Simple Moving Average).
%D = SMA[D] of %K
The default periods in chart are 14 days for %K, and 3 days smoothing for %D. The %K line is drawn in red and the %D line in green.
%K and %D just described are called the “fast” stochastics. Corresponding “slow” stochastics are formed by smoothing %K with a simple moving average, and calculating %D from that smoothed series. The extra smoothing is the “slow days” parameter in Chart. The default is 0 for no slowing, a value of 3 is often used.
Incidentally, a value of 1 for the slowing is the same as no slowing, because a 1-period SMA of course doesn’t change the data.
Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2014, 2015, 2016, 2017 Kevin Ryde
Chart is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.