Categories:

Aggregate functions (Linear Regression) , Window functions

# REGR_R2Â¶

Returns the coefficient of determination for non-null pairs in a group. It is computed for non-null pairs using the following formula:

```NULL                 if VAR_POP(x) = 0, else
1                    if VAR_POP(y) = 0 and VAR_POP(x) <> 0, else
POWER(CORR(y,x), 2)
```

Where `x` is the independent variable and `y` is the dependent variable.

## SyntaxÂ¶

Aggregate function

```REGR_R2(y, x)
```

Window function

```REGR_R2(y, x) OVER ( [ PARTITION BY <expr3> ] )
```

## ArgumentsÂ¶

`y`

The dependent variable. This must be an expression that can be evaluated to a numeric type.

`x`

The independent variable. This must be an expression that can be evaluated to a numeric type.

`expr3`

This is the optional expression used to group rows into partitions.

Important

Note the order of the arguments; the dependent variable is first.

## Usage notesÂ¶

• DISTINCT is not supported for this function.

• When used as a window function:

• This function does not support:

• ORDER BY sub-clause in the OVER() clause.

• Window frames.

## ExamplesÂ¶

```create or replace table aggr(k int, v decimal(10,2), v2 decimal(10, 2));
insert into aggr values(1, 10, null);
insert into aggr values(2, 10, 11), (2, 20, 22), (2, 25,null), (2, 30, 35);
```
```select k, regr_r2(v, v2) from aggr group by k;

---+----------------+
k | regr_r2(v, v2) |
---+----------------+
1 | [NULL]         |
2 | 0.9976905312   |
---+----------------+
```
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