The aggregate node

The aggregate node lets you compute statistical functions on data_batches. This node can compute multiple statistic functions on multiple fields.

See nodes under /nodes/statistics for details (Not all of these are available here).

This node can only take data_batch items, so in most cases you will need some kind of batch or window node to collect batches.

The aggregate node produces a new stream of data consisting of data_point items.

Example

|value_emitter()
.every(1s)
.type('point') 

|win_time()
.every(15s)

|aggregate()
.fields('val', 'val', 'val', 'val')
.functions('variance', 'sum', 'avg', 'count_distinct')
.as('variance', 'sum', 'average', 'count_distinct')

|debug()

Parameters

Parameter	Description	Default
fields( string_list )	names of the fields used for each computation
functions( string_list )	list of function names (see 'Functions' table below for possible values)
as( string_list )	names for the fields for output values	defaults to the name of the compute function
keep( string_list )	fields that should be kept from the input data-items	[]
keep_tail( boolean )	keep the last data-point from every incoming batch, so it can be used for count_change as inital value	true

Functions

Name	Description	Note
sum	computes the sum of all values	numerical values only
avg	computes the average of all values	numerical values only
min	computes the minimum value
max	computes the maximum value
mean	computes the mean value	numerical values only
median	computes the median value	numerical values only
first	outputs the first (oldest) value
last	outputs the last (newest) value
count	outputs the total number of values
count_distinct	outputs the number of unique values
count_change	outputs the number of value changes for the given field	with keep_tail set to true, the last item will serve as initial value
range	computes the range	between minimum and maximum
variance	computes the variance	numerical values only
stddev	computes the standard deviation of the values	numerical values only
skew	computes the skew of all values	numerical values only