frequency_table_with_null

aggregation-functions frequency_table_with_null

syntax

frequency_table_with_null(a)
frequency_table_with_null(a, relation)

definition

frequency_table_with_null(a) results in a parameter with a string listing all values of attribute a — including null values — together with how often each value occurs, separated by “; “.
frequency_table_with_null(a, relation) results in an attribute with such strings, one per partition defined by relation. The domain-unit of the resulting attribute is the values-unit of the relation. Each partition string contains the value-count pairs for all values of a (including null) belonging to that partition.

description

The result per partition is a string of the form value1: count1; value2: count2; ..., where:

values are listed in ascending order (the order defined by the values-unit of attribute a),
only values with a non-zero count are included,
null values in a are included in the frequency table and are shown as <null>: count.

This function is identical to frequency_table except that null values in a are counted and included in the result string. Elements mapped to a null partition (null relation value) are still excluded from all groups.

applies to

attribute a with any scalar value-type
relation with value type of the group CanBeDomainUnit

conditions

The domain of argument a and relation must match.

since version

14.4.0

example

parameter<string> freqLifeStyleCodeWithNull := frequency_table_with_null(City/LifeStyleCode);
// result = "0: 2; 1: 3; 2: 1; <null>: 1"

attribute<string> freqLifeStyleCodeWithNullPerRegion (Region) := frequency_table_with_null(City/LifeStyleCode, City/Region_rel);

City/LifeStyleCode	City/Region_rel
2	0
0	1
1	2
0	1
1	3
1	null
null	3

domain City, nr of rows = 7

freqLifeStyleCodeWithNullPerRegion
“2: 1”
“0: 2”
“1: 1”
“1: 1; <null>: 1”
”“

domain Region, nr of rows = 5

City 6 (LifeStyleCode = null, Region_rel = 3) is included in Region 3’s count as <null>: 1. City 5 (Region_rel = null) is excluded from all groups.