sample_variance
Description
Returns the sample variance of a numerical expression within a group.
- Useful for analyzing variability when working with incomplete datasets.
- Designed for scenarios like heavy trace sampling, where global variance would be misleading.
Note
Use sample_variance
when only a subset of data is available. For complete datasets, prefer variance
.
Syntax
Arguments
Name | Type | Required | Description |
---|---|---|---|
expression | number | true | Numerical expression whose sample variance is computed |
Example
Use case: Compute variance of trace durations
Suppose you want to calculate how much the duration of each operation varies across traces, even when the dataset is incomplete.
Example data
{ "operationName": "cart", "duration": 50000 },
{ "operationName": "checkout", "duration": 200000 },
{ "operationName": "brokenPrinter", "duration": 700000 },
{ "operationName": "SendOrderConfirmation", "duration": 10200 },
{ "operationName": "cart", "duration": 300000 },
{ "operationName": "brokenPrinter", "duration": 1000000 },
{ "operationName": "checkout", "duration": 900000 },
{ "operationName": "cart", "duration": 600000 },
{ "operationName": "brokenPrinter", "duration": 400000 },
{ "operationName": "SendOrderConfirmation", "duration": 9950 },
{ "operationName": "checkout", "duration": 1200000 },
{ "operationName": "cart", "duration": 100000 },
{ "operationName": "brokenPrinter", "duration": 20000 },
{ "operationName": "SendOrderConfirmation", "duration": 10050 },
{ "operationName": "checkout", "duration": 1500000 },
{ "operationName": "cart", "duration": 800000 },
{ "operationName": "brokenPrinter", "duration": 800000 },
{ "operationName": "checkout", "duration": 500000 },
{ "operationName": "SendOrderConfirmation", "duration": 10100 },
{ "operationName": "cart", "duration": 400000 }
Example query
Example output
operationName | duration_variance |
---|---|
brokenPrinter | 56413398108.59468 |
cart | 70558342573.80327 |
checkout | 111286897989.06136 |
SendOrderConfirmation | 383221.0732801104 |
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