应该是用来设定什么时候使用新的pattern.

PATTERNID=BY | GROUP | MIDPOINT | SUBGROUP
specifies the way fill patterns are assigned. By default, PATTERNID=SUBGROUP. Values for PATTERNID= are as follows:

BY
changes patterns each time the value of the BY variable changes. All bars use the same pattern if the GCHART procedure does not include a BY statement.

GROUP
changes patterns every time the value of the group variable changes. All bars in each group use the same pattern, but a different pattern is used for each group.

MIDPOINT
changes patterns every time the midpoint value changes. If you use the GROUP= option, the respective midpoint patterns are repeated for each group.

SUBGROUP
changes patterns every time the value of the subgroup variable changes. The bars must be subdivided by the SUBGROUP= option for the SUBGROUP value to have an effect. Without SUBGROUP=, all bars have the same pattern.

3Q