Series

What is a Series?

A Series is a named array that grows bar by bar. You write a value at the current bar with .set() and read past values with .get(offset). Unlike regular JavaScript variables that reset on each onBar call, a Series persists across bars.

const prevEma = Series("prev-ema");

onBar(() => {
  const ema = ta.ema(ctx.close, 14);
  const prev = prevEma.get(1); // EMA from previous bar

  // Detect EMA crossing above its own prior value
  if (!na(prev) && ema > prev) {
    plot("Signal", ctx.low() - ctx.atr); // placeholder
  }

  prevEma.set(ema); // store for next bar
});

API reference

Series object

Create a named series. Must be called at the top level (not inside onBar). Up to 64 series per script.

const s = Series("my-series");

void

Store value at the current bar index. Call inside onBar.

s.set(ctx.close());
</ParamField>

<ParamField path="s.get(offset?)" type="number">
Read the value at `offset` bars back. `offset = 0` (default) is the current bar. Returns `NaN` for bars where `.set()` was never called.
```js
const current = s.get();    // current bar
const prev    = s.get(1);   // 1 bar ago
const twoBack = s.get(2);   // 2 bars ago

number

Number of bars where .set() has been called.

Budget

Maximum 64 Series per script (shared with any hidden series created internally by ta.barssince and ta.cum).
Each series consumes roughly 8 KB per bar in the window.
Total budget across all series: ~512 KB per script.

Creating Series inside onBar mid-execution is allowed syntactically, but the series will have no backfill - it starts empty from the bar it was first created. For correct historical replay, always create Series at the top level.

Worked example: crossover detection

// Detect when the fast EMA crosses above the slow EMA
const fastSeries = Series("fast-ema");
const slowSeries = Series("slow-ema");

plot("Fast EMA", null, { color: "#22c55eFF" });
plot("Slow EMA", null, { color: "#f59e0bFF" });
plot("Cross", null, { style: "arrowup", colorUp: "#22c55eFF", size: 10 });

onBar(() => {
  const fast = ta.ema(ctx.close, 9);
  const slow = ta.ema(ctx.close, 21);

  const prevFast = fastSeries.get(1);
  const prevSlow = slowSeries.get(1);

  fastSeries.set(fast);
  slowSeries.set(slow);

  plot("Fast EMA", fast);
  plot("Slow EMA", slow);

  // Crossover: fast was below slow, now above
  const crossover = !na(prevFast) && !na(prevSlow) && prevFast < prevSlow && fast > slow;
  plot("Cross", crossover ? ctx.low() * 0.999 : NaN);
});

No-backfill behavior

A Series created mid-script (e.g. inside a conditional block on bar 500) has no values for bars 0-499. s.get(offset) returns NaN for those bars. Plan accordingly using na(s.get(...)) guards.

NaN handling

Series.get() returns NaN during warmup.

Aggregators

ta.barssince and ta.cum use internal series with a key.

API limits

64-series budget shared with stateful aggregators.

Getting Started

Core Concepts

Plotting

Drawing Entities

Technical Analysis

Utility Namespaces

Examples

Reference

What is a Series?

API reference

Budget

Worked example: crossover detection

No-backfill behavior

NaN handling

Aggregators

API limits

​What is a Series?

​API reference

​Budget

​Worked example: crossover detection

​No-backfill behavior

​Related pages

NaN handling

Aggregators

API limits

What is a Series?

API reference

Budget

Worked example: crossover detection

No-backfill behavior

Related pages