Mass Index — how much the range is expanding relative to its own recent
expansion, summed over a window.
The ratio of a 9-bar EMA of the range to a 9-bar EMA of that is near 1 while
volatility is steady and rises as the range widens, so the sum reads as
"volatility has been building for a while" rather than "this bar was wide".
The nested EMA is the parity trap in this file: its input is already na for
the first 8 bars, and the reference reseeds past that rather than propagating it, which
is why the plot starts two warmups plus a window deep.
Mass Index — how much the range is expanding relative to its own recent expansion, summed over a window.
The ratio of a 9-bar EMA of the range to a 9-bar EMA of that is near 1 while volatility is steady and rises as the range widens, so the sum reads as "volatility has been building for a while" rather than "this bar was wide". The nested EMA is the parity trap in this file: its input is already
nafor the first 8 bars, and the reference reseeds past that rather than propagating it, which is why the plot starts two warmups plus a window deep.