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 + Composite + 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.
For example, server uptime is usually measured using a counter metric. Here is how the raw data looks before applying the function:
Upon applying the Delta function, we can easily monitor even minor anomalies in the change rate of the server uptime:
Note: In case the metric value increases monotonically and occasionally resets to zero (e.g., on restart), use the NonNegativeDelta function instead.