Jerk is the third step in a chain of rolling regressions. The first fits a straight line to the source over the last Period bars and takes its slope, the trend's speed. The second fits a line to that slope series, giving acceleration. The third fits a line to the acceleration series, and its slope is the plotted jerk.
Each fit is a rolling least squares line over the last Period bars, where the x value is the bar number. The sums behind it are kept as running totals: each bar adds the newest point and removes the one that left the window. A bar whose value is absent still takes its place in the window but adds nothing to the sums, and a slope needs at least two valid points.
Each stage starts once the stage before it has produced two values, so the jerk line begins on the fourth bar of the chart.
How to read Acceleration, Slope of Slope (JERK)
Jerk above zero means acceleration is rising; below zero it is falling. Its zero crossings mark the turning points of acceleration, which tend to come ahead of the turning points of the slope, which in turn come ahead of the trend. That makes it an early but noisy warning that the character of a move is shifting.
Each derivative amplifies noise, so expect a busy line on short periods and fast charts. The values are in price units per bar cubed and scale with the instrument, so compare readings only within one chart.
Settings
- Period
- The number of bars each of the three regression lines is fitted over. A longer period gives a smoother, slower line.
- Source
- The price series the first regression is fitted to, the close by default.
Frequently asked questions
What does jerk add over acceleration?
Acceleration tells you whether the trend is speeding up. Jerk tells you whether that speeding up is itself increasing or fading, so it turns before acceleration does, at the cost of more noise.
Why is the line so noisy?
Every regression stage measures a rate of change of the stage before it, and each one magnifies small wiggles. A longer period calms all three stages at once.
