> ## Documentation Index
> Fetch the complete documentation index at: https://docs.oxla.com/llms.txt
> Use this file to discover all available pages before exploring further.

# REGR_R2()

The `REGR_R2()` aggregate function calculates the coefficient of determination (R<sup>2</sup>) for a linear regression model. The R<sup>2</sup> value indicates how well the independent variable (x) explains the variability of the dependent variable (y).

## Syntax

The syntax for this function is as follows:

```sql theme={null}
REGR_R2(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
<a href="https://www.postgresql.org/ftp/projects/pgFoundry/dbsamples/pagila/pagila/" target="_blank">Pagila</a> database website.

```sql theme={null}
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);
```

The query below uses the `REGR_R2()` function to calculate the coefficient of determination (R<sup>2</sup>) for valid pairs of `rating` and `length`:

```sql theme={null}
SELECT
    REGR_R2(rating, length) AS coefficientOfDetermination
FROM film;
```

By running the above code, we're going to get the following output:

```sql theme={null}
 coefficientofdetermination 
----------------------------
         0.3832337818693347
(1 row)
```