Bar Chart

Type: bar_chart • Category: visualization

Description

Append categorical/time point to a bar chart widget

Parameters

Name	Type	Description	Required	Default
widgetId	string		no
pointExpr	string	Expr -> {value: number, ts?: epoch_ms, category?: str}	no
limit	number		no	500

Help

Overview

The Append Point to Bar Chart worker enriches an existing bar‑chart widget by adding a new data point that can include a numeric value, an optional timestamp, and an optional categorical label. This is useful for visualising financial‑market information such as price updates, volume spikes, or event markers directly on a bar chart.

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Inputs

• widgetId – string
  Identifier of the target bar‑chart widget that will receive the new point.

• pointExpr – string (expression)
  An expression that evaluates to an object with the following shape:

  {
    "value": number,          // required numeric value to plot
    "ts": epoch_ms?,          // optional Unix timestamp in milliseconds
    "category": "string"?     // optional categorical label (e.g., “Earnings”, “Dividend”)
  }

• limit – number (optional, default = 500)
  Maximum number of points the widget will retain after the insertion. If the widget already contains limit points, the oldest entry is discarded to make room for the new one.

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Minimal Example Usage

{
  "widgetId": "chart-42",
  "pointExpr": "{ value: 125.7, ts: 1728000000, category: \"Earnings\" }",
  "limit": 300
}

In this example the worker:

1. Locates the bar‑chart widget with ID chart-42.
2. Evaluates pointExpr to obtain a point {value: 125.7, ts: 1728000000, category: "Earnings"}.
3. Appends the point to the chart, ensuring the total number of points does not exceed 300 (oldest points are removed if necessary).