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 |