StatisticalPlots`

BoxOutlierMarkers

is an option for BoxWhiskerPlot that specifies markers to be used for outliers.

Details and Options

To use BoxOutlierMarkers, you first need to load the Statistical Plots Package using Needs["StatisticalPlots`"].
Valid settings are the same as for PlotMarkers.
With the setting BoxOutlierMarkers->Automatic, the outliers are drawn as points.
With the setting BoxOutlierMarkers->None, the outliers are not drawn.
The setting BoxOutlierShapes->{g₁,g₂} can be used to specify g₁ as markers for near outliers and g₂ as markers for far outliers.

Use triangles for near outliers and squares for far outliers:

Top