Appendix F: Sum functions

The sum functions detect anomalies when the sum of a field in a bucket is anomalous.

If you want to monitor unusually high totals, use high-sided functions.

If want to look at drops in totals, use low-sided functions.

If your data is sparse, use non_null_sum functions. Buckets without values are ignored; buckets with a zero value are analyzed.

The machine learning features include the following sum functions:

The sum function detects anomalies where the sum of a field in a bucket is anomalous.

If you want to monitor unusually high sum values, use the high_sum function.

If you want to monitor unusually low sum values, use the low_sum function.

These functions support the following properties:

For more information about those properties, see the create anomaly detection jobs API.

Example 1: Analyzing total expenses with the sum function.

{
  "function" : "sum",
  "field_name" : "expenses",
  "by_field_name" : "costcenter",
  "over_field_name" : "employee"
}

If you use this sum function in a detector in your anomaly detection job, it models total expenses per employees for each cost center. For each time bucket, it detects when an employee’s expenses are unusual for a cost center compared to other employees.

Example 2: Analyzing total bytes with the high_sum function.

{
  "function" : "high_sum",
  "field_name" : "cs_bytes",
  "over_field_name" : "cs_host"
}

If you use this high_sum function in a detector in your anomaly detection job, it models total cs_bytes. It detects cs_hosts that transfer unusually high volumes compared to other cs_hosts. This example looks for volumes of data transferred from a client to a server on the internet that are unusual compared to other clients. This scenario could be useful to detect data exfiltration or to find users that are abusing internet privileges.

The non_null_sum function is useful if your data is sparse. Buckets without values are ignored and buckets with a zero value are analyzed.

If you want to monitor unusually high totals, use the high_non_null_sum function.

If you want to look at drops in totals, use the low_non_null_sum function.

These functions support the following properties:

For more information about those properties, see the create anomaly detection jobs API.

Example 3: Analyzing employee approvals with the high_non_null_sum function.

{
  "function" : "high_non_null_sum",
  "field_name" : "amount_approved",
  "by_field_name" : "employee"
}

If you use this high_non_null_sum function in a detector in your anomaly detection job, it models the total amount_approved for each employee. It ignores any buckets where the amount is null. It detects employees who approve unusually high amounts compared to their past behavior.