# Reducers

Juttle reducers operate on batches of points, carrying out a running computation over values contained in the points, optionally over a moving time window.

Reducers can be used as the right-hand side of put expressions, in which case they compute a result over points in the current batch as each new point arrives. They can also be used as the right-hand side of reduce expressions, in which case they compute a result over points in the current batch when the batch ends. For options that govern all reducers, see put and reduce.

Juttle comes with built-in reducers:

Return the average of the values of a specified field.

Return the number of points in the stream, optionally filtering on a specified field.

Return the total number of unique values of a specified field throughout the batch.

Return the change in value of a field.

Return the value of the specified field in the first point that contains it.

Return the value of the specified field for the last point that contains it.

Return the Median Absolute Deviation (MAD) of the value of the specified field.

Return the maximum value of the specified field from among all points containing that field.

Return the minimum value of the specified field from among all points containing that field.

Return the p

Return an array of the values of a specified field in the batch.

Return the standard deviation of the value of the specified field.

Return the sum of the values of the specified field throughout the batch.