The BOXPLOT Procedure

In a schematic box plot, outlier values within a group are plotted as separate points beyond the whiskers of the box-and-whiskers plot. See the section Styles of Box Plots and the description of the BOXSTYLE= option for a complete description of schematic box plots.

The following statements use the BOXSTYLE= option to produce a schematic box plot of the data from the Turbine data set. The OUTBOX= option creates a summary data set named OilSchematic.

title 'Schematic Box Plot for Power Output';
ods graphics on;
proc boxplot data=Turbine;
   plot KWatts*Day / boxstyle = schematic
                     outbox   = OilSchematic;
run;

The schematic box plot is shown in Figure 4. Note the outliers plotted for several of the groups.

Figure 4: Schematic Box Plot of Power Output

Whereas the Oilsum data set from the section Creating Box Plots from Summary Data contains a variable for each summary statistic and one observation per group, the OUTBOX= data set OilSchematic contains one observation for each summary statistic in each group. The _TYPE_ variable identifies the statistic and the _VALUE_ variable contains its value. In addition, the OilSchematic data set contains an observation that records each outlier value for each group. Figure 5 shows a partial listing of the OilSchematic data set.

Observations with the _TYPE_ variable values "HIGH" and "LOW" contain outlier values. If you want to use a summary data set to re-create a schematic box plot, you must create an OUTBOX= data set in order to save the outlier data.