Non-null standard deviation (biased) (nnstddev)
This operation calculates the biased standard deviation of the non-null values found in a specified column for each grouping occurrence. If you want to include null values, you can use the Standard deviation (biased) (stddev) operation and if you want to calculate the unbiased variant, you can use the Non-null standard deviation (unbiased) (nnustddev) operation.
How does it work in the search window?
Before being able to perform this operation, you have to group your data. Be aware that the columns used as arguments for the grouping operation will not be available to select as arguments for the aggregation operation.
After grouping the data, select Aggregation in the search window toolbar, then select the Non-null standard deviation (biased) operation. You need to specify one argument:
|Biased standard deviation of (mandatory)||integer, float|
The data type of the aggregated values is integer or float.
siem.logtrust.web.activity table, we want to calculate the biased standard deviation of the non-null values found in the responseLength column during each 5-minute period. Before aggregating the data, the table must be grouped in 5-minute intervals. Then we will perform the aggregation using the Non-null standard deviation (biased) operation.
The arguments needed for the Non-null standard deviation (biased) operation are:
- Biased standard deviation of → responseLength column
Click Aggregate function and you will see the following result:
How does it work in LINQ?
Group your data using the following structure:
as... to add the new column that will show the aggregated values. This is the syntax for the Non-null standard deviation (biased) operation:
See Build a query using LINQ to learn more about grouping and aggregating your data using the LINQ language.
You can copy the following LINQ script and try the example above on the
from siem.logtrust.web.activity group every 5m every 5m select nnstddev(responseLength) as responseLength_nnstddev