relationalai.std.math.erf()

erf(number: Number|Producer) -> Expression

Calculates the error function of number, commonly used in probability, statistics, and partial differential equations. If number is a Producer, erf() filters out any non-numeric values from the producer. Must be called in a rule or query context.

Parameters

Name	Type	Description
number	Producer or Python Number object	The value to calculate the error function of.

Returns

An Expression object.

Example

Use erf() to calculate the error function of a number:

import relationalai as rai
from relationalai.std import math


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

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

with model.rule():
    Measurement.add(id=1).set(value=0.5)
    Measurement.add(id=2).set(value=1.0)
    Measurement.add(id=3).set(value="INVALID")  # Non-numeric value


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

# Set an erf_value property to the error function of each measurement's value.
with model.rule():
    measurement = Measurement()
    measurement.set(erf_value=math.erf(measurement.value))

# Since erf() filters out non-numeric values, the erf_value property
# is not set for the measurement with id=3.
with model.query() as select:
    measurement = Measurement()
    response = select(measurement.id, measurement.erf_value)

print(response.results)
#    id  erf_value
# 0   1   0.520500
# 1   2   0.842701
# 2   3        NaN

See Also

• erfinv()