a '{kind}' rolling column needs an 'orderBy' column to define its order - the screen sort is never used, because a rolling figure would then change on every header click. It reported null until an orderBy is set.

Warnings reference › grid.rolling.orderBy:*:*

Identifier

grid.rolling.orderBy:*:*

Raised by

The grid (core)

Since

1.29.0

What happened

A rolling figure - a running total, a moving average, a lag - is defined by an order, and that order is deliberately not the grid's current sort: reading it from the screen would make every cell change when a user clicks a header. With no orderBy the figure is undefined, so the column reports null for every row.

The fix

Name the column that defines the series order.

The smallest fix

columns: [{ id: 'runningTotal', rolling: { kind: 'sum', of: 'amount', orderBy: 'date' } }]

Reference

Covered in full at the API reference.