Multiplication (*) operator

	Double	Long	Text	Categorical	Date
Double	Multiply Double	Multiply Double	Multiply1 Double	Not applicable	Multiply2 Date
Long	Multiply Double	Multiply Long	Multiply1 Long	Intersection Categorical	Multiply 2 Date
Text	Multiply1 Double	Multiply4 Double5	Not applicable	Intersection 3 Categorical	Multiply4 Date
Categorical	Not applicable	Intersection Categorical	Intersection3 Categorical	Intersection Categorical	Not applicable
Date	Multiply2 Date	Multiply2 Date	Multiply4 Date	Not applicable	Multiply Date

visits is an integer (Long) variable and genbalance is a real (Double) weighting variable. This expression multiplies the values in the two variables and compares whether the result is greater than 1.

The biology and education variables are single response categorical variables that have identical category lists (Yes, No, and Not answered). The * operator performs an intersection of the two category lists, which means that it returns the categories that are in both of the category lists. The = operator tests whether the result is the Yes category. For example, you could use this expression to select respondents who chose the Yes category in response to both questions.

The * operator is generally useful for categorical variables only if they have identical or overlapping category lists.