intercept()

Calculate the y-intercept from a counter aggregate

Since 1.3.0

Calculate the y-intercept of a linear least-squares fit between counter value and time. This corresponds to the projected value at the Postgres epoch (2000-01-01 00:00:00+00). You can use the y-intercept with the slope to plot a best-fit line.

Samples

Calculate the y-intercept of the linear fit for each 15-minute counter aggregate.

SELECT
    id,
    bucket,
    intercept(summary)
FROM (
    SELECT
        id,
        time_bucket('15 min'::interval, ts) AS bucket,
        counter_agg(ts, val) AS summary
    FROM foo
    GROUP BY id, time_bucket('15 min'::interval, ts)
) t

Arguments

The syntax is:

intercept(
    summary CounterSummary
) RETURNS DOUBLE PRECISION

Name	Type	Default	Required	Description
summary	CounterSummary	-	✔	A counter aggregate created using counter_agg

Returns

Column	Type	Description
intercept	DOUBLE PRECISION	The y-intercept of the linear least-squares fit