Correlation

aggregation-functions correlation

syntax

  • corr(a, b)
  • corr(a, b, relation)

definition

  • corr(a, b) results in the correlation coefficient of attributes a and b.
  • corr(a, b, relation) results in the correlation coefficient of attributes a and b, grouped by relation. The domain-unit of the resulting attribute is the values-unit of the relation.

The value-type of the resulting data-item is float32 or float64.

applies to

  • attribute a and b with Numeric value-type
  • relation with value type of the group CanBeDomainUnit

conditions

  1. The value type of the arguments a and b must match.
  2. The domain of arguments a, b and relation must match.

example 

1. parameter<float32> corrNrInhabitantsTemp                := 
    corr(float32(City/NrInhabitants), City/avgDailyTemperature); result = -0.89948
2. attribute<float32> corrNrInhabitantsTempRegion (Region) :=
    corr(
       float32(City/NrInhabitants)
      ,City/avgDailyTemperature
      ,City/RegionNr
   );
City/NrInhabitants City/avgDailyTemperature City/Region_rel
550 12 0
525 11 1
300 null 2
500 11 1
200 14 3
175 null null
null 14 3

domain City, nr of rows = 7

corrNrInhabitantsTempRegion
null
null
null
null
null

domain Region, nr of rows = 5