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Covariancebeforereadingbasicsyntaxcrystalsyntax

Returns the covariance value of the field which defines the measure of linear coherence of two field values.

Covariance( fld1, fld2 )
Covariance( fld1, fld2, condFld )
Covariance( fld1, fld2, condFld, cond )

fld1	The first of two fields needed for calculating the covariance.
fld2	The second of two fields needed for calculating the covariance.
condFld	The name of the field that groups the values of fld (if fld isn't an array).
cond	A string declaring the type of grouping to be used on condFld. This only makes sense for groups based on Date, DateTime, Time, and Boolean fields. See Summary Field Conditions for a list of strings you can use here.

A fractional number.

//calculates the coherence of the count of the average income and the average output.
Covariance({Prod.income},{Prod.output})

//calculates the same coherence, but grouped by time
Covariance({Prod.income},{Prod.output}, {Prod.messurment_time})

If the values in fld should be grouped, a group based on condFld is needed. If the group does not exist in the report, you can add it using i-net Designer or using API method: Engine.addGroup.
An undefined covariance due to a variance of zero will result in a value of 1.