If the first observation in the input data set to PROC BOXPLOT has a missing value for the group variable and there are two or more observations in the group following the missing group, and if you specify the MISSBREAK option on the PLOT statement, then the first two box-and-whisker plots will be incorrect. The first observation with a nonmissing value of the group variable is incorrectly treated as its own group, and a box-and-whisker plot is created from this single observation. The next box-and-whisker plot will be incorrect because its first observation has been omitted. INSETGROUP and OUTBOX= data set statistics will also be incorrect for the first two box-and-whisker plots since they were created by splitting one consecutive set of group values into two groups. Similarly, if BY processing is done and the first observation in any BY group has missing group variable value, the following group will incorrectly be split into two box-and-whisker plots if it contains two or more observations. This results in incorrect INSETGROUP and OUTBOX= data set statistics for the first two box-and-whisker plots for that BY group as well.

To circumvent this problem, delete the first observation in the data set or in any BY group if it has a missing value for the group variable.