4.5 Wildcard

Wildcard can be used in field names. For example, when using the sum function to compute the total across multiple fields with numeric labels, wildcard can be use to simplify the listing of all fields as one label. For example, if there are three columns are named A1,A2,A3 in the input data, the total sum of A1,A2,A3 can be calculated as sum(${A*}). It is also possible to specify multiple wildcard such as the expression sum(${A*},${B*}).