Every day, compare price to its 200-day average, and remember every past ratio. The colored bands are the 5th through 95th percentile of that history — an expanding “how unusual is this stretch?” cone.
The lower pane is a 0–100 rank: 5 means only 5% of history was cheaper vs the 200-day; 95 means almost everything was cheaper (i.e. you are stretched). Green is cheap vs that distribution; red is stretched.
Daily grid (linear fill of missing calendar days). Expanding window of P/SMA_200, min 200 observations. Quantiles Q5, Q10, Q25, Q50 (=200DMA), Q75, Q90, Q95. Oscillator = percentile rank of today’s ratio in that buffer.
r_t = P_t / SMA_200_t. band_q,t = Q_q({r_s : s≤t}) · SMA_200_t.
osc_t = 100 · #{ r_s ≤ r_t } / n_t (percentile rank).
Log y2 cannot plot 0 — marker color uses true quantile, y uses max(q,1). Window starts at first valid quantile date.