Why is nothing plotted in the Box Plot graph for a group that has only one unique data point?.

Why is nothing plotted in the Box Plot graph for a group that has only one unique data point?

Description:
  When there is only one data point (or only one unique value), the Box Plot will only plot the horizontal line for the Median. The default color for the Box Plot’s median line is the same as the visualization’s default background color, so it appears as if nothing has been plotted.

Symptom:
  Box Plot in graph appears to be missing,

Cause:
  The default color for the Box Plot's median line is the same as the visualization's default background color. To make the median line visible when there is only one unique value, do the following:

1). Right-click on the Box Plot and select “Properties” from the context sensitive menu.
2). Select “Reference Points” in the left pane of the “Box Plot Properties” dialog (note that the current color for Median is white).
3). Select a color for the Median line that will contrast with both the visualization’s background color and the populated boxplot's color.

Note that the default color for the Box Plot’s median line is the same as the visualization’s default background color:

Right-click on the Box Plot and select “Properties” from the context sensitive menu:

Select “Reference Points” in the left pane of the “Box Plot Properties” dialog, and note that the current color for Median is white:

Select a color for the Median line that will contrast with both the visualization’s background color and the populated boxplots’ color:

Here, the median lines are all shown in red: