Anchored PVI + NVIAnchored PVI + NVI is a single-pane indicator that allows the Positive Volume Index (PVI) and Negative Volume Index (NVI) to be plotted together using a period-anchored approach. Crucially, the EMAs for each series are included and remain analytically valid under the anchoring process.
PVI and NVI are cumulative, path dependent indicators. Over long histories, their absolute values become arbitrary and often incomparable when plotted side-by-side . This script addresses that limitation by anchoring each indicator to a user-defined period (daily, weekly, monthly, etc.) and plotting their relative change from that baseline rather than their raw values.
The result is a clean, comparable view that preserves each indicator’s internal structure (trends, inflections, divergences, and EMA relationships) while minimizing scale conflicts.
**What Are PVI and NVI? (Quick Explanation)**
PVI and NVI separate price behavior based on changes in participation, not raw volume flow.
- Positive Volume Index (PVI) updates only on bars where volume increases relative to the prior bar. It tracks price movement during expanding participation, often associated with broad market involvement.
- Negative Volume Index (NVI) updates only on bars where volume decreases relative to the prior bar. It tracks price movement during contracting participation, often associated with quieter or more selective activity.
Both indicators accumulate percentage price changes, but only under their respective volume conditions. Rather than asking “Is volume high or low?” , they ask:
"How does price behave when participation expands versus when it contracts?"
More detailed guidance and interpretation can be found further down the publication description for users unfamiliar with the practical uses of PVI and NVI.
**How The Script Works**
At the start of each selected anchor period, the script records the current PVI and NVI values as baselines. All subsequent values within that period are plotted as changes relative to those baselines:
- Percent mode plots the percentage change from the baseline.
- Absolute mode plots the absolute change from the baseline.
This is not normalization or rescaling. The time-based shape of each series is preserved within the anchor window.
The EMAs are calculated on the original, full-history PVI and NVI series, then transformed using the same anchored reference frame. This faithfully preserves relative positioning between each index and its EMA, EMA slope behavior, and EMA crossover timing.
Optional anchor markers and a zero line help visualize resets and behavior relative to the period’s starting point.
**Advantages vs Using PVI and NVI Separately**
- Faster visual assessment: Participation-conditioned price behavior can be evaluated at a glance without mentally reconciling separate scales or panes.
- Potential for Extended Interpretation: A shared baseline introduces a form of relative comparability that does not exist when the indicators are plotted independently.
- Cleaner workflow: One indicator, one pane, and less chart clutter.
**Conventional Interpretation and Guidance**
Anchored PVI and NVI should be interpreted relative to the zero line, their own EMAs, and each other, always within the context of the current anchor period - NOT across periods.
Values above zero indicate net positive price movement since the anchor began under the indicator’s respective volume condition. Values below zero indicate net negative movement. Because PVI and NVI update under different participation regimes, their behavior provides complementary context rather than redundant confirmation.
When PVI is rising, price progress within the period is occurring primarily during higher-participation sessions. This suggests that movement is being supported by expanding activity. Weakness or flattening in PVI indicates that price is losing traction during high-volume conditions.
When NVI is rising, price persistence is occurring during quieter sessions as participation contracts. This often reflects continuation or structural stability that does not rely on broad engagement. Weakness in NVI indicates that price struggles to hold together as activity declines.
Comparing the two provides insight into participation balance.
- Both rising: broad support across participation regimes
- PVI rising while NVI lags: movement concentrated in higher-participation sessions
- NVI rising while PVI lags: price persistence despite reduced participation
Each index is most commonly interpreted relative to its own 255-period EMA. Holding above the EMA suggests strengthening behavior within that participation regime, while sustained movement below the EMA indicates weakening momentum or transition. NVI in particular is often interpreted such that above-EMA behavior is supportive and below-EMA behavior is cautionary.
Divergence between price and PVI or NVI can highlight changes in participation dynamics that may not yet be reflected in price alone. Divergence between PVI and NVI themselves highlights shifts in how price behaves under expanding versus contracting participation.
These relationships are best used as contextual confirmation rather than as standalone trading signals.
**Extended Interpretation (Exploratory)**
This section is exploratory and should not be interpreted as conventional or widely-accepted guidance.
Anchoring PVI and NVI to a shared baseline introduces a form of relative comparability that does not exist when the indicators are plotted independently.
Within a single anchor period, both PVI and NVI are now expressed as relative change from a common reference point. This makes it possible to observe how the two series interact directly in time.
Index Crossovers (PVI vs. NVI)
Crossovers between anchored PVI and anchored NVI may be interpreted as shifts in dominance between participation regimes within the anchor period.
- PVI crossing above NVI suggests that price progress under expanding participation has overtaken progress under contracting participation since the anchor began.
- NVI crossing above PVI suggests that price persistence during quieter participation has become the dominant contributor within the period.
EMA-to-EMA Structure (PVI EMA vs. NVI EMA)
EMA-to-EMA relationships can further highlight smoother, regime-level tendencies in participation balance. When one EMA persistently leads the other after sufficient post-anchor price action has accumulated, it reflects a sustained bias toward that participation regime within the anchor window. Similarly, EMA crossovers that develop after sufficient post-anchor data may imply a transition in participation balance rather than a reset artifact.
Important Context and Limitations of Extended Interpretation
This form of interpretation is only valid within a single anchor period. Because each anchor resets the baseline, no continuity or meaning should be inferred across different periods.
These interactions should be treated as descriptive of participation balance, not as standalone trade signals. Their value lies in clarifying how price movement is being carried within a defined window, not in predicting future direction.
**Combined Practical Use**
Altogether, this indicator allows participation dynamics to be evaluated at three levels:
1) Instantaneous behavior via the anchored PVI and NVI themselves
2) Structural persistence via each index relative to its own EMA
3) Regime balance via the relative positioning of PVI, NVI, and their EMAs
**Warnings!**
- Percent mode can become visually unstable when baseline PVI or NVI values are near zero due to division effects inherent in percent-change calculations.
**Other Similar Indicators**
My Anchored OBV + A/D script applies the same anchored-period framework to other volume-based indicators.
**Credits**
This script is inspired by Multi-Ticker Anchored Candles (MTAC) by @SamRecio . MTAC's anchored-baseline concept and open-source nature provided an important conceptual foundation for adapting the same idea to PVI and NVI.
Indikator Pine Script®
