ewma Metrics Operator

The ewma operator computes an Exponentially Weighted Moving Average (EWMA) on the data points returned by the query for the selected time range. This allows you to smooth out short-term fluctuations (outliers) and display long-term trends.

You can optionally run ewma with either:

• An explicit alpha smoothing parameter to smooth time series while preserving trends. This is useful if you want to explicitly set the smoothing parameter value.
• A span over a number of points. The span parameter is commonly understood as an N-Day Exponentially Weighted Moving Average. The span value is the number of data points that will be used to calculate the average. The decay (smoothing) parameter alpha is related to span as: alpha = 2/(span + 1)

The most commonly used parameter is span, which allows you to specify the number of data points you want to use for smoothing. The higher the value of span, the smoother the time series will be. You might choose to use alpha if you know what smoothing parameter value you want use. Keep in mind that the lower the alpha value is, the smoother the time series will be.

If you run ewma without specifying either alpha or span, it runs by default with alpha=0.5 (orspan=3).

Syntax

ewma [alpha=<decimal> | span=<integer>]

Where:

• alpha, the smoothing parameter, is a decimal value (0.0 ≤ alpha ≤ 1.0) The default value of alpha is 0.5
• span is the number of data points. Must be a positive integer. If you set span=5, the last five data points will be used to calculate the average. The default value of span is 3.

Examples

Using alpha

metric=CPU_Idle | ewma alpha=0.1

Using span

metric=CPU_Idle | ewma span=10