Parameters, controls and actions

Parameters

A parameter is a named value a reader can change. Create it, give it a default, and optionally allow multiple values.

On its own it does nothing — something must reference it: a filter, a calculated field, a URL action, or a title.

Controls

A parameter becomes visible by adding a control — dropdown, list, slider, date picker or text box.

A dropdown can be populated from a field in a dataset, so it stays current as the data changes rather than needing manual maintenance.

Using parameters

// dynamic threshold in a calculated field
ifelse({Revenue} > ${MinRevenue}, 'Above', 'Below')

// dynamic measure selection
ifelse(${Metric} = 'Revenue', sum({Revenue}), sum({Units}))

The measure-swap pattern lets one chart display whichever metric the reader picks, rather than building three charts.

Parameters can also appear in visual titles, so the heading reflects the current selection.

Filters versus parameters

A filter restricts data directly. A parameter supplies a value that something else uses.

Use a filter to narrow the data; use a parameter when the selection should change what the analysis does — swap a measure, move a threshold, drive a reference line.

Actions

Actions wire visuals together:

As elsewhere, restraint matters. Two or three well-chosen actions get used; a dashboard where everything filters everything is disorienting.