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Computes the coefficient of determination (also referred to as R-squared or the goodness-of-fit statistic) for the regression line.
REGR_R2(dependent-expression, independent-expression)
REGR_R2(dependent-expression, independent-expression)
OVER (window-spec)
window-spec: See Syntax 2 instructions in the Usage section below.
dependent-expression The variable that is affected by the independent variable.
independent-expression The variable that influences the outcome.
This function converts its arguments to DOUBLE, performs the computation in double-precision floating-point, and returns a DOUBLE as the result. If applied to an empty set, then REGR_R2 returns NULL.
REGR_R2 is applied to the set of (dependent-expression and independent-expression) pairs after eliminating all pairs for which either dependent-expression or independent-expression is NULL. Sybase IQ then applies the following algorithm:
REGR_R2 calculates VAR_POP(x) and returns NULL if VAR_POP(x) = 0; otherwise, it calculates VAR_POP(y) and returns the value 1 if VAR_POP(y) = 0.
If neither VAR_POP(x) or VAR_POP(y) is zero, the return value is POWER(CORR(y,x),2)
where y represents the dependent-expression and x represents the independent-expression.
See "Mathematical formulas for the aggregate functions "in SQL Anywhere Server – SQL Usage.
ROLLUP and CUBE are not supported in the GROUP
BY clause with Syntax 1. DISTINCT is not supported.
Syntax 2 represents usage as a window function in a SELECT statement. As such, you can specify elements of window-spec either in the function syntax (inline), or with a WINDOW clause in the SELECT statement. For information on how to specify the window, see “Analytical functions”.
The following example returns the value 0.19379959710325653:
SELECT REGR_R2( Salary, ( YEAR( NOW() ) - YEAR( BirthDate ) ) )FROM Employees;
