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NUnique

Approximate number of unique values counter.

This is basically an implementation of the HyperLogLog algorithm. Adapted from hypy. The code is a bit too terse but it will do for now.

Parameters

  • error_rate

    Type → float

    Default → 0.01

    Desired error rate. Memory usage is inversely proportional to this value.

  • seed

    Type → int | None

    Default → None

    Set the seed to produce identical results.

Attributes

  • n_bits (int)

  • n_buckets (int)

  • buckets (list)

Examples

import string
from river import sketch

alphabet = string.ascii_lowercase
n_unique = sketch.NUnique(error_rate=0.2, seed=42)

n_unique.update('a')
n_unique.get()

1


n_unique.update('b')
n_unique.get()

2


for letter in alphabet:
    n_unique.update(letter)
n_unique.get()

31

Lowering the error_rate parameter will increase the precision.

n_unique = sketch.NUnique(error_rate=0.01, seed=42)
for letter in alphabet:
    n_unique.update(letter)
n_unique.get()

26

Methods

get
update

References