JoinAggregate Transform

The joinaggregate transform extends the input data objects with aggregate values. Aggregation is performed and the results are then joined with the input data. The parameters for this transform are nearly identical to the aggregate transform, but rather than creating new output objects, the results are written back to each of the input data objects. A joinaggregate can also be written with the window transform by setting the frame to [null, null]. This transform can be helpful for creating derived values that combine both raw data and aggregate calculations, such as percentages of group totals.

Transform Parameters

Property Type Description
groupby Field[ ] The data fields to group by. If not specified, a single group containing all data objects will be used.
fields Field[ ] The data fields for which to compute aggregate functions. This array should align with the ops and as arrays. If no fields and ops are specified, a count aggregation will be used by default.
ops String[ ] The aggregation operations to apply to the fields, such as sum, average or count. See the aggregate operation reference for more.
as String[ ] The output field names to use for each aggregated field in fields. If not specified, names will be automatically generated based on the operation and field names (e.g., sum_field, average_field).

Aggregate Operation Reference

All valid aggregate operations.

Operation Description
count The total count of data objects in the group.
valid The count of field values that are not null, undefined or NaN.
missing The count of null or undefined field values.
distinct The count of distinct field values.
sum The sum of field values.
mean The mean (average) field value.
average The mean (average) field value. Identical to mean.
variance The sample variance of field values.
variancep The population variance of field values.
stdev The sample standard deviation of field values.
stdevp The population standard deviation of field values.
stderr The standard error of field values.
median The median field value.
q1 The lower quartile boundary of field values.
q3 The upper quartile boundary of field values.
ci0 The lower boundary of the bootstrapped 95% confidence interval of the mean field value.
ci1 The upper boundary of the bootstrapped 95% confidence interval of the mean field value.
min The minimum field value.
max The maximum field value.
argmin An input data object containing the minimum field value.
argmax An input data object containing the maximum field value.


For the following input data:

  {"foo": 1, "bar": 1},
  {"foo": 1, "bar": 2},
  {"foo": null, "bar": 3}

The join aggregate transform

  "type": "joinaggregate",
  "fields": ["foo", "bar", "bar"],
  "ops": ["valid", "sum", "median"],
  "as": ["v", "s", "m"]

produces the output:

  {"foo": 1, "bar": 1, "v": 2, "s": 6, "m": 2},
  {"foo": 1, "bar": 2, "v": 2, "s": 6, "m": 2},
  {"foo": null, "bar": 3, "v": 2, "s": 6, "m": 2}