These pages outline the chart configuration options, and the methods and properties of Highcharts objects.
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Format for points with the value of null. Works analogously to
format. nullFormat can
be applied only to series which support displaying null points.
heatmap and tilemap supports nullFormat by default while the
following series requires [#series.nullInteraction] set to true:
line, spline, area, area-spline, column, bar, and
timeline. Does not work with series that don't display null
points, like pie.