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relationalai.std.math.log2()

log2(value: Number|Producer) -> Expression

Calculates the base-2 logarithm of value. If value is a Producer, log2() filters out any non-numeric or negative values from the producer. Must be called in a rule or query context.

Parameters

Name	Type	Description
`value`	`Producer` or Python `Number` object	The number to take the base-2 logarithm of.

Returns

An Expression object.

Example

Use log2() to calculate the base-2 logarithm of a number:

import relationalai as rai
from relationalai.std import math


# =====
# SETUP
# =====

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

with model.rule():
    Person.add(id=1).set(name="Alice", age=16)
    Person.add(id=2).set(name="Bob", age=-8)  # Negative age
    Person.add(id=3).set(name="Carol", age="INVALID")  # Non-numeric age


# =======
# EXAMPLE
# =======

# Set an age_log2 property to the base-2 logarithm of each person’s age.
with model.rule():
    person = Person()
    person.set(age_log2=math.log2(person.age))

# Since log2() filters out negative and non-numeric values, the age_log2
# property is not set for Bob or Carol.
with model.query() as select:
    person = Person()
    response = select(person.id, person.name, person.age_log2)

print(response.results)
#    id     name  age_log2
# 0   1    Alice       4.0
# 1   2      Bob       NaN
# 2   3    Carol       NaN

See Also