Used to generate a trendline for a periodic dataset. The key parameter
period specifies the length of the period to be applied. This is used
after a timechart, as in timechart(...) |
holtwinters(1week). The function implements
triple
exponential smoothing, and adds an extra graph for every series in
the graph. The computation assumes periodic data set (the period parameter
specifies the length of the period), such as daily or weekly traffic
measurements. The function works best when the timecharts span (width of
each bucket) is a multiple of the period, as the smoothing is done in
units of the buckets.
For example, a 30 day chart with a 7 day period would have 4 periods from day 2 to 30 (the first 2 days being ignored). Based on this, the first 3 periods (in this case period 1, 2 and 3) are fed into the smoothing/forecast computation, producing a "forecast" for the fourth period. Smoothing data for period 2, 3 and 4 are emitted, the last period being entirely computed.
| Parameter | Type | Required | Default | Description |
|---|---|---|---|---|
alpha | number | false | Data smoothing factor in the interval [0..1]. | |
beta | number | false | Trend smoothing factor in the interval [0..1]. | |
gamma | number | false | Seasonal change smoothing in the interval [0..1]. | |
period | string | true | Defines the trend's period, such as 1week or 1day |---| see the full list of the allowed time periods at Relative Time Syntax. [a] | |
[a] When you provide only one parameter, the implied parameter is | ||||
Examples
Show event count graph with daily aggregates and compute the weekly trend.
timechart(function=count(), span=1d) | holtwinters(period=7d)