Variance

syntax

var(a)
var(a, relation)

definition

var(a) results in a parameter with the variance of the non null values of attribute a.
var(a, relation) results in an attribute with the variance of the non null values of attribute a, grouped by relation. The domain-unit of the resulting attribute is the values-unit of the relation].

description

The variance is calculated as the square of the sum of the differences of each value and the mean value of the distribution. This square is divided by the number of values (n).

This way of calculating the variance is different from e.g. the ms Excel VAR function, which divides the sum of the differences by n-1.

applies to

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

conditions

The value-type of argument a and the resulting data-item must match.
The domain of arguments a and relation must match.

example

1. parameter<float32> varNrInh                := var(float32(City/NrInhabitants)); result = 24166.67
2. attribute<float32> varNrInhRegion (Region) := var(float32(City/NrInhabitants), City/Region_rel);

City/NrInhabitants	City/Region_rel
550	0
525	1
300	2
500	1
200	3
175	null
null	3

domain City, nr of rows = 7

varNrInhRegion
0
156.25
0
0
null

domain Region, nr of rows = 5