REGR_AVGY()

Overview

The REGR_AVGY() aggregate function calculates the mean of the dependent variable (y) for non-null pairs of dependent (y) and independent (x) variables. This function is used in linear regression analysis to compute the average value of the dependent variable where both variables are not null.

Syntax

The syntax for this function is as follows:

REGR_AVGY(y, x)

Parameters

• y: variable being predicted
• x: variable used for prediction

Example

For the needs of this section, we’re going to use a simplified version of the film table from the Pagila database, containing only the title, length and rating columns. The complete schema for the film table can be found on the Pagila database website.

DROP TABLE IF EXISTS film;
CREATE TABLE film (
  title text NOT NULL,
  length int,
  rating int
);
INSERT INTO film(title, length, rating) VALUES
  ('ATTRACTION NEWTON', 83, 5),
  ('CHRISTMAS MOONSHINE', 150, 7),
  ('DANGEROUS UPTOWN', 121, 4),
  ('KILL BROTHERHOOD', 54, 3),
  ('HALLOWEEN NUTS', 47, 5),
  ('HOURS RAGE', 122, 7),
  ('PIANIST OUTFIELD', 136, 7),
  ('PICKUP DRIVING', 77, 3),
  ('INDEPENDENCE HOTEL', 157, 7),
  ('PRIVATE DROP', 106, 4),
  ('SAINTS BRIDE', 125, 3),
  ('FOREVER CANDIDATE', 131, 7),
  ('MILLION ACE', 142, 5),
  ('SLEEPY JAPANESE', 137, 4),
  ('WRATH MILE', 176, 7),
  ('YOUTH KICK', 179, 7),
  ('CLOCKWORK PARADISE', 143, 5);

They query below uses the REGR_AVGY() function to calculate the mean of the dependent variable (rating) for rows where both rating and length are not null:

SELECT
    REGR_AVGY(rating, length) AS AverageRating   
FROM film;

By running the above query, we will get the following output:

   averagerating   
-------------------
 5.294117647058823
(1 row)