avg()#

relationalai.std.aggregates
avg(*args: Producer, per: Optional[List[Producer]]) -> Expression

Calculates the average of values produced by one or more Producer objects. Pass a list of Producer objects to the optional per parameter to group values and compute the average per group. Must be called in a rule or query context.

Parameters#

NameTypeDescription
*argsProducerOne or more Producer objects.

Returns#

An Expression object.

Example#

import relationalai as rai
from relationalai.std import aggregates

model = rai.Model("people")
Person = model.Type("Person")

with model.rule():
    Person.add(name="Joe", age=41)
    Person.add(name="Jane", age=39)

with model.query() as select:
    person = Person()
    avg_age = aggregates.avg(person.age)
    response = select(avg_age)

print(response.results)
# Output:
#    result
# 0    40.0

person.age represents the set of all ages in the model. If two people have the same age, you must pass the person instance, in addition to person.age, to avg() so that each person contributes to the average:

import relationalai as rai
from relationalai.std import aggregates

model = rai.Model("people")
Person = model.Type("Person")

with model.rule():
    Person.add(name="Joe", age=41)
    Person.add(name="Jane", age=39)
    Person.add(name="John", age=41)

with model.query() as select:
    person = Person()
    avg_age = aggregates.avg(person, person.age)
    response = select(avg_age)

print(response.results)
# Output:
#       result
# 0  40.333333

When the query is evaluated, all pairs of person objects and their age properties are produced, and the average of the age values is computed. You may pass any number of Producer objects to avg(). The aggregation occurs over the values produced by the last argument.

To group values and compute the average for each group, pass one or more Producer objects to the optional per parameter as a list. In the following example, the person object is passed to per to compute the average age of a person’s friends:

import relationalai as rai
from relationalai.std import aggregates

model = rai.Model("friends")
Person = model.Type("Person")

with model.rule():
    joe = Person.add(name="Joe", age=41)
    jane = Person.add(name="Jane", age=39)
    john = Person.add(name="John", age=41)
    joe.set(friend=jane).set(friend=john)
    jane.set(friend=joe)
    john.set(friend=joe)

with model.query() as select:
    person = Person()
    avg_friend_age = aggregates.avg(person.friend, person.friend.age, per=[person])
    response = select(person.name, avg_friend_age)

print(response.results)
# Output:
#    name  result
# 0  Jane    41.0
# 1   Joe    40.0
# 2  John    41.0

See Also#