Rolling z-score — how many rolling standard deviations the value sits
from its rolling mean: (value − SMA(period)) / stdev(period) (population
stdev). Appends one column; undefined on the warm-up and on any flat
(σ = 0) window. One rolling pass (mean + stdev).
Rolling z-score — how many rolling standard deviations the value sits from its rolling mean:
(value − SMA(period)) / stdev(period)(population stdev). Appends one column;undefinedon the warm-up and on any flat (σ = 0) window. One rolling pass (mean + stdev).