Tooltip Fields

tooltip_fields adds extra rows to a chart’s hover tooltip without dropping to custom_echart. Each field is an aggregate (or GROUP BY–safe) SQL expression that Evidence appends to the chart’s query and renders as an extra row under the primary value.

Example

{% bar_chart
    data="orders"
    x="month"
    y="sum(total_sales)"
    y_fmt="usd"
    tooltip_fields=[
        { value="count(distinct order_id)" label="Orders" },
        { value="sum(total_sales) / nullif(count(distinct order_id), 0)" label="Avg order" fmt="usd" }
    ]
/%}

Fields

Field	Required	Description
`value`	Yes	SQL expression to show in the tooltip, e.g. `"sum(share)"`. Must be an aggregate or a `GROUP BY`–safe column — it runs under the same `GROUP BY`, filters, and date range as the chart’s primary `y`.
`label`	No	Text shown to the left of the value. Defaults to a title-cased version of the expression.
`fmt`	No	Format code applied to the value (e.g. `"usd"`, `"pct1"`, `"num0"`, or an Excel-style custom format). Defaults to `num`.
`color_by_sign`	No	Colour the value green when ≥ 0 and red when < 0. Defaults to `false`.
`down_is_good`	No	Flip the sign colouring so negatives are green and positives red. Only applies when `color_by_sign=true`. Defaults to `false`.

Syntax

This is Markdoc, not JSON — the separator rules differ:

Object properties are separated by spaces, not commas: { value="sum(x)" label="X" fmt="usd" }
Array elements are separated by commas: [{ … }, { … }]
Strings use double quotes; booleans are bare (color_by_sign=true).

Do not put commas between properties inside an object — { value="x", label="y" } will fail to parse. Commas belong only between array elements.

Map layers

point_layer and area_layer take a simpler form — an array of column-name strings:

{% point_layer data="plants" lat="lat" long="long"
    tooltip_fields=["fuel_type", "capacity_mw", "emissions"]
/%}

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Example

Fields

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Map layers