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.0
• 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

parameter<float32> corrNrInhabitantsTemp                := 
  corr(float32(City/NrInhabitants), City/avgDailyTemperature); result = -0.89948
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