Open interest

Open interest is the optional oi field on a Bar. It is the number of contracts outstanding at that observation, not traded volume. An omitted reading means unknown; 0 means the feed reported zero.

Supply readings and add studies

Provide a container with id="chart". Import the indicator tier to register the built-in OI studies; custom feeds can supply oi through the same series API.

import { createChart } from 'openalgo-charts';
import 'openalgo-charts/indicators';
 
const chart = createChart(document.getElementById('chart')!);
chart.setDataContext({
  symbol: 'CONTRACT', exchange: 'DEMO', interval: '1m', hasOpenInterest: true,
});
chart.setStatusLineOptions({ openInterest: true });
const series = chart.addSeries('candlestick');
series.setData([
  { time: 60, open: 100, high: 103, low: 99, close: 102, volume: 20, oi: 140 },
  { time: 120, open: 102, high: 104, low: 101, close: 103, volume: 10, oi: 150 },
  { time: 180, open: 103, high: 104, low: 101, close: 102, volume: 15 },
]);
chart.addIndicator('open-interest');
chart.addIndicator('open-interest-change');
chart.fitContent();

The final bar produces a gap in the OI line. It does not add a zero reading or reuse the preceding bar’s value. See the live OI example.

Study ID	Output
`open-interest`	Pane line with plot key `oi` and compact quantity formatting.
`open-interest-change`	Pane histogram with plot key `change`, showing adjacent OI differences. The first reading and a pair containing missing OI are null.
`open-interest-buildup`	Main candle colors from adjacent price and OI changes. It adds no price plot or axis.

Buildup classifies long buildup, short buildup, short covering and long unwinding, with color inputs longBuildupColor, shortBuildupColor, shortCoveringColor and longUnwindingColor. Its calculated state is 1, 2, 3 or 4 in that order. Missing readings leave the candle’s own color. The default unchanged: 'neutral' leaves zero changes neutral; 'up' treats them as nonnegative. Line and histogram styles use the normal generated plot controls.

Capability is separate from data

ChartDataContext.hasOpenInterest and chart.hasOpenInterest have three states:

Value	Meaning
`true`	The instrument supports OI. A particular bar may still lack a reading.
`false`	The instrument does not support OI.
`undefined`	The host has not supplied capability metadata.

Do not infer capability from zero or an absent forming-bar reading. The OI status-line preference defaults off; enabling it shows a field only when a reading exists. Explicitly unsupported capability suppresses the field without clearing that preference. The preference survives chart state restoration; instrument capability must be supplied again from current host metadata.

InstrumentAdapter can apply the same capability with the instrument’s calendar and price rules. The widget retains it for an interval change on the same instrument and clears it when symbol or exchange changes. See instruments and crosshair and legend.

Aggregation, live updates and replay

Historical aggregation sums volume and retains the latest defined OI within each bucket. If none of its source bars contains OI, the bucket has no reading; it never borrows a level from the preceding bucket. securitySeries exposes a nullable oi column with the same developing/confirmed-bucket timing as its price columns. Enabling lookahead has the same future-data implications.

Live CandleBuilder and TickBarAggregator replace OI with each finite tick reading. A tick that omits OI clears the forming bar’s prior value, so a stale historical position is not presented as a fresh observation. A delayed history reply preserves the newer live observation, including absence or zero.

Heikin Ashi retains OI because each output maps to one input bar. Price-generated Renko, Range, Line Break, Point and Figure and Kagi bars omit it. Arithmetic expressions also omit OI: combining contract prices does not define one contract’s position size. During partial replay, only revealed sub-bars contribute OI; the final candle’s reading appears at its completion.

Feed adapters and persistence

Adapters should omit unavailable or nonfinite OI and retain genuine zero values. OpenAlgoConfig.hasOpenInterest(request) can explicitly return false to remove an unsupported instrument’s placeholder history column. The callback receives the actual request, so it can handle concurrent instruments independently. The bundled OpenAlgo quote adapter does not supply live OI; do not manufacture a current value from its historical reading.

Closed-bar caches preserve valid optional readings and reject malformed levels. Chart configuration snapshots store preferences and studies, not bar history. The host remains responsible for restoring the appropriate data and capability. CSV export writes oi as its own column with blank missing cells and unchanged zero values.

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