Delta

Description

 Transforms each sample in the time series to the difference between the sample and the previous one.

Input

Time Series: Multiple (Single or multiple time-series) 

Parameters

 Keep Last Value Limit

Optional, numeric, default=null (Limit of null values to skip) 

Output

Transformed Time Series: Multiple 

Available in

Alerts, Composites, Dashboards 

The Delta function is useful when you have a metric whose value increases monotonically. By applying this function, you can monitor the difference between two successive samples in the metric, and catch anomalous changes in the increase rate. 

Usage Example

Server uptime is usually measured using a counter metric. This chart shows some raw data before applying the function:  

Delta0.png

 

After applying the Delta function, even minor anomalies can be easily monitored in the change rate of the server uptime:  

Delta1.png


Note: In cases where the metric value increases monotonically and occasionally resets to zero (for example, on restart), use the NonNegativeDelta function instead. 

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