# noDataValue

Calendar heatmap: what a day without entries reads — a number (default 0 → the ramp's first colour) or `nan` (→ `empty-color`).

Canonical: https://chart.syidax.com/docs/options/noDataValue/

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## Definition

| Item | Value |
| --- | --- |
| JavaScript property | `noDataValue` |
| HTML attribute | Pass objects, arrays, and callbacks as JavaScript properties |
| Type | `number \| 'nan'` |
| Default | `undefined` |
| Literals in the type | `nan` |

undefined means this property was not explicitly set. The effective value may depend on the chart type and other settings.

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## Related documentation

A property with the same name may have different types and defaults across charts. When using a direct tag, follow that chart's documentation below.

- [Shared facade and direct tags](https://chart.syidax.com/docs/concepts.md)
- [sy-calendar-heatmap](https://chart.syidax.com/docs/components/calendar-heatmap.md#property-noDataValue)