diff --git a/docs/querying/functions.md b/docs/querying/functions.md index d4236f0b86..5f0774136b 100644 --- a/docs/querying/functions.md +++ b/docs/querying/functions.md @@ -136,6 +136,8 @@ delta(cpu_temp_celsius{host="zeus"}[2h]) `deriv(v range-vector)` calculates the per-second derivative of the time series in a range vector `v`, using [simple linear regression](https://en.wikipedia.org/wiki/Simple_linear_regression). +The range vector must have at least two samples in order to perform the calculation. When `+Inf` or +`-Inf` are found in the range vector, the slope and offset value calculated will be `NaN`. `deriv` should only be used with gauges. @@ -335,6 +337,9 @@ January etc. `predict_linear(v range-vector, t scalar)` predicts the value of time series `t` seconds from now, based on the range vector `v`, using [simple linear regression](https://en.wikipedia.org/wiki/Simple_linear_regression). +The range vector must have at least two samples in order to perform the +calculation. When `+Inf` or `-Inf` are found in the range vector, +the slope and offset value calculated will be `NaN`. `predict_linear` should only be used with gauges.