The correlation coefficient of the least squares fit line of the adjusted counter value and epoch value of the time column. Given that the slope of a line for any counter value must be non-negative, this must also always be non-negative and in the range from 0.0 to 1.0. It measures how well the least squares fit the available data, where a value of 1.0 represents the strongest correlation between time and the counter increasing.
corr( summary CounterSummary ) RETURNS DOUBLE PRECISION
For more information about counter aggregation functions, see the hyperfunctions documentation.
|summary||CounterSummary||The input CounterSummary from a counter_agg call|
|corr||DOUBLE PRECISION||The correlation coefficient computed from the least squares fit of the adjusted counter values input to the CounterSummary|
SELECT id, bucket, corr(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
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