chart x column "{col}" is a 'date', which stores a calendar day, so all {n} rows collapsed into one point and were reduced by '{fn}'. For a series inside a single day, type the column 'datetime' or bind epoch milliseconds.

Warnings reference › chart:x:date-bucket:*

Identifier

chart:x:date-bucket:*

Raised by

Charts

Since

1.70.0

What happened

A date column stores YYYY-MM-DD, so sub-day timestamps arrive as copies of one day and the reduction runs over the lot: one point whose value totals things that were never meant to be totalled. The resolution is gone before the chart sees it. For a type that scales its x there is no series left to draw and the picture is refused; a *bar* of one day's total is an honest reduction and still draws. The binder notices the collapse and the drawability pass decides the picture - both report under this one key, so an integrator reads one line.

The fix

Type the column 'datetime' (or 'timestamp'), or bind epoch milliseconds, so the readings keep their time of day.

The smallest fix

columns: [{ id: 'at', type: 'datetime' }]

Reference

Covered in full at the API reference.