Linear regression functions:

REGR_AVGX(Y, X) = SUM(X) / N

REGR_AVGY(Y, X) = SUM(Y) / N

REGR_COUNT(Y, X) = N

REGR_INTERCEPT(Y, X) = REGR_AVGY(Y, X) - REGR_SLOPE(Y, X) * REGR_AVG_X(Y, X)

REGR_R2(Y, X) = POWER(CORR(Y, X),2)

REGR_SLOPE(Y, X) = COVAR_POP(Y, X)

REGR_SXX(Y, X) = N * VAR_POP(X)

REGR_SXY(Y, X) = N * COVAR_POP(Y, X)

REGR_SYY(Y, X) = N * VAR_POP(Y)

Contributed by Hajime Nakagami.

Github pull request:

https://github.com/FirebirdSQL/core/pull/4