# ROC-of-ROC Also known as: acceleration. A Momentum & Oscillators concept (Rate-of-change cluster) in the LuxAlgo Library, with 1 indicator implementation. ## What is ROC-of-ROC? ROC-of-ROC applies [rate of change](https://www.luxalgo.com/library/concept/roc/) twice: it measures how fast the speed of price movement is itself changing. In the physics analogy, price is position, [momentum](https://www.luxalgo.com/library/concept/momentum/) or ROC is velocity, and ROC-of-ROC is acceleration. The second derivative is positive while momentum builds, crosses zero the moment momentum stops building, and turns negative while momentum decays, which can happen well before price itself stops rising. The appeal is lead time: in an idealized cycle each derivative turns before the one below it, so acceleration rolls over before momentum, which rolls over before price. The cost is noise, because differencing amplifies the fastest fluctuations in a series and doing it twice compounds that. Practical versions smooth the inputs or the output, and treat the reading as context for [trend acceleration and inflection](https://www.luxalgo.com/library/concept/trend-acceleration-inflection/) rather than as a standalone trigger. Construction is two lookbacks and a smoothing plan. The inner ROC's period sets which momentum is being differentiated, the outer period sets how the change in that momentum is measured, and where the smoothing goes, on price before the first difference, on the momentum line between them, or on the final output, decides how much of the doubled noise survives. The same recipe generalizes beyond price: differentiating an oscillator, the RSI-acceleration constructions, asks whether that indicator's move is quickening or tiring, with identical mathematics and identical noise economics. Reading discipline keeps the tool honest. Acceleration's zero cross marks, in principle, the momentum extremum, which is earlier than any momentum signal but also the most falsifiable moment on the chart; divergences between price extremes and acceleration extremes extend the standard swing logic one derivative up; and the [MACD](https://www.luxalgo.com/library/concept/macd/) histogram's expansion and contraction encodes closely related information, since the spread between two smoothed momenta changes fastest exactly when thrust builds or fades. Everything second-derivative belongs in the context layer: it grades the move's vigor, and structure still decides the trade. ## How to identify ROC-of-ROC readings Two lookbacks, a smoothing plan, and one interpretive rule: sign of acceleration versus state of momentum. 1. Choose the inner lookback: the ROC whose changes you care about, commonly a short-to-medium momentum window. 2. Smooth the input or the momentum line, because differencing twice without smoothing yields mostly bar noise. 3. Apply the outer ROC: the change in the smoothed momentum over its own lookback, which is the acceleration reading. 4. Smooth the output lightly if the line still chatters, accepting that every pass delays the lead the construction exists to provide. 5. Read sign against state: positive acceleration in a rising market is thrust building, negative acceleration under new price highs is the early-fade warning, and the zero cross approximates the momentum peak. ## How it's calculated A second-order momentum reading that shows whether momentum itself is accelerating or decelerating. ``` ROC_t = 100 × (P_t - P_t-n1) / P_t-n1 RocRoc_t = ROC_t - ROC_t-n2 P_t: price at bar t, usually the close n1: lookback of the first ROC in bars (commonly 10) n2: lookback of the second stage in bars (commonly 10, often set equal to n1) ROC_t: percent rate of change of price over n1 bars RocRoc_t: ROC-of-ROC, the n2-bar change in the first ROC t: current bar ``` Positive readings mean momentum is accelerating and negative readings mean it is fading, which can lead price turns while price still trends. Some scripts apply the percent ROC formula literally to the first ROC series; because ROC crosses zero that version is unstable, so the point-difference second stage is the usual form. Output is in percentage points of ROC; a short moving average is often added to reduce noise. ## How traders use it - As an early deceleration warning: price pressing to new highs while acceleration is already negative shows the thrust behind the move fading, a cue to tighten risk rather than an automatic reversal call. - As a thrust-quality check at breakouts: strongly positive acceleration on the breakout distinguishes impulsive moves from grinding drifts. - As an earlier zero-cross trigger: acceleration flips sign around the point where momentum peaks, ahead of momentum's own zero cross, but it fires many false starts, so it is usually smoothed and confirmed by other evidence. - On other indicators: the same double-differencing applied to an oscillator, RSI acceleration being the common build, asks whether that gauge's move is quickening or exhausting, one derivative earlier than the gauge itself answers. - As a cross-check against histogram dynamics: expanding and contracting [MACD](https://www.luxalgo.com/library/concept/macd/) histogram bars encode kindred second-derivative information, and agreement between the two constructions is worth more than either alone. ## ROC-of-ROC vs related momentum derivatives - **ROC** (https://www.luxalgo.com/library/concept/roc/): First versus second derivative: ROC says how fast price moved, ROC-of-ROC says whether that speed is growing or shrinking. Each step up the derivative ladder buys earliness and pays double in noise, which is the entire economics of the family. - **MACD** (https://www.luxalgo.com/library/concept/macd/): The histogram is a cousin: the changing spread between two smoothed momenta widens and narrows with thrust, second-derivative-flavored information delivered with MACD's built-in smoothing. ROC-of-ROC is the raw version, faster, noisier, and unbounded by design choices. - **Trend Acceleration/Inflection** (https://www.luxalgo.com/library/concept/trend-acceleration-inflection/): The same physics read from a different proxy: curvature analysis differentiates a smoothed trend line, ROC-of-ROC differentiates percentage momentum. Curvature is steadier and later, the double-ROC twitchier and earlier; both feed the same phase-labeling discipline. ## FAQ ### What does ROC-of-ROC actually measure? It measures the change in the rate of change: not whether price is rising, and not how fast, but whether that speed is increasing or decreasing. A rally can show positive momentum with negative acceleration, meaning it is still going up but more slowly each bar. That distinction is the entire content of the indicator. ### Why is ROC-of-ROC so noisy, and what helps? Differencing a series amplifies its fastest fluctuations, and ROC-of-ROC differences price twice, so bar-to-bar noise dominates the raw output. Common fixes are smoothing price before the first ROC, smoothing the final line, or lengthening both lookbacks. Every fix adds lag, which eats into the early-warning property that motivated the second derivative in the first place. ### Is the MACD histogram the same as acceleration? Related, not identical. The histogram tracks the changing gap between two smoothed momentum proxies, so its expansion and contraction carries second-derivative-like information with MACD's smoothing built in; ROC-of-ROC differentiates explicitly and inherits explicit noise. In practice they nominate similar moments, thrust building, thrust fading, and their agreement is a reasonable filter on either one's false starts. ### What lookbacks should the two ROCs use? No standard exists, and the noise economics dominate the choice: short inner windows track tradable momentum but demand smoothing, while the outer window mostly sets how briskly acceleration responds. Common practice keeps both short, single digits to low teens, and spends the saved lag budget on a smoothing pass. Whatever the numbers, calibrate on the instrument, because acceleration's usable signal-to-noise varies wildly across markets. ### Can acceleration be computed on indicators instead of price? Yes, and it is a standard construction: differentiate RSI, an average, or any smooth-enough series and you get that gauge's acceleration, asking whether its move is quickening or tiring one derivative early. The builds that work start from already-smoothed inputs, since differencing a jagged oscillator twice yields static. The reading grammar transfers unchanged: sign versus state, zero crosses at the input's extrema, divergences one level up. ### Does acceleration really lead price? In clean cyclical motion, yes, by construction: each derivative peaks a quarter-cycle before the one below, so acceleration rolls over first. Real markets deliver that lead statistically rather than reliably, buried in noise and regime shifts, and the zero crosses that would be prescient in a sine wave arrive in bursts of false starts on a chart. The defensible use is contextual: acceleration grades thrust and flags early fatigue, while entries wait for structure. ## Implementations in the Library - ROC-of-ROC (LuxAlgo): https://www.luxalgo.com/library/indicator/roc-of-roc/ ## Related concepts - Momentum: https://www.luxalgo.com/library/concept/momentum/ - Disparity Index: https://www.luxalgo.com/library/concept/disparity-index/ - ROC: https://www.luxalgo.com/library/concept/roc/ - Chande Momentum Oscillator: https://www.luxalgo.com/library/concept/chande-momentum-oscillator/ - Know Sure Thing: https://www.luxalgo.com/library/concept/know-sure-thing/ - Coppock Curve: https://www.luxalgo.com/library/concept/coppock-curve/ - Detrended Price Oscillator: https://www.luxalgo.com/library/concept/detrended-price-oscillator/ - TRIX: https://www.luxalgo.com/library/concept/trix/ - Psychological Line: https://www.luxalgo.com/library/concept/psychological-line/ - Special K: https://www.luxalgo.com/library/concept/special-k/ --- Source: https://www.luxalgo.com/library/concept/roc-of-roc/ (LuxAlgo Library, the encyclopedia of trading & technical analysis). Free to use with attribution: https://www.luxalgo.com/library/license/