linReg( ) Query Function

Computes a linear relationship model between two variables using least-squares fitting. Given variables x and y, the relationship is y = slope * x + intercept. The result is output in fields named _slope and _intercept - unless a different prefix than _ is specified. Also output are the adjusted R-squared value _r2 and the number of data points _n. No output is produced, however, if all x values are the same or if all y values are the same.

Parameters

Name Type Required Default Description
x string Yes The name of the field containing the independent variable.
y string Yes The name of the field containing the dependent variable.
prefix string No _ Prefix for the names of all the output fields.

linReg has no unnamed parameter.

Examples

Find the correlation between the bytes sent in a server response and the time to send them.

linReg(x=bytes_sent, y=send_duration)

Find the correlation between server load and total reponse size across time.

bucket(function=[ sum(bytes_sent, as=x), avg(server_load_pct, as=y) ]) | linReg(x=x, y=y)

Find the correlation between server load and each of several types of request types across time.

bucket(function=[ avg(server_load_pct, as=y), groupby(request_type, function=count(as=x)) ]) | groupby(request_type, function=linReg(x=x, y=y))