slope()

Since 1.3.0

Calculate the slope of the linear least-squares fit for a counter aggregate. The dependent variable is the counter value, adjusted for resets, and the independent variable is time. Time is always in seconds, so the slope estimates the per-second rate of change. This gives a result similar to rate, but it can more accurately reflect the usual counter behavior in the presence of infrequent, abnormally large changes.

Samples

Calculate the counter slope per id and per 15-minute interval.

SELECT
    id,
    bucket,
    slope(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:

slope(
    summary CounterSummary
) RETURNS DOUBLE PRECISION

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

Returns

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