slope()

Calculate the slope from a counter aggregate

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.

Arguments

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

Returns

DOUBLE PRECISION: The slope of the linear least-squares fit

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