# AnomalySine¶

Simulate a stream with anomalies in sine waves

The data generated corresponds to sine (attribute 1) and cosine (attribute 2) functions. Anomalies are induced by replacing values from attribute 2 with values from a sine function different to the one used in attribute 1. The contextual flag can be used to introduce contextual anomalies which are values in the normal global range, but abnormal compared to the seasonal pattern. Contextual attributes are introduced by replacing values in attribute 2 with values from attribute 1.

## Parameters¶

• n_samples (int) – defaults to 10000

Number of samples

• n_anomalies (int) – defaults to 2500

Number of anomalies. Can't be larger than n_samples.

• contextual (bool) – defaults to False

If True, will add contextual anomalies

• n_contextual (int) – defaults to 2500

Number of contextual anomalies. Can't be larger than n_samples.

• shift (int) – defaults to 4

Shift in number of samples applied when retrieving contextual anomalies

• noise (float) – defaults to 0.5

Amount of noise

• replace (bool) – defaults to True

If True, anomalies are randomly sampled with replacement

• seed (int) – defaults to None

If int, seed is used to seed the random number generator; If RandomState instance, seed is the random number generator; If None, the random number generator is the RandomState instance used by np.random.

## Attributes¶

• desc

Return the description from the docstring.

## Examples¶

>>> from river import synth

>>> dataset = synth.AnomalySine(seed=12345,
...                             n_samples=100,
...                             n_anomalies=25,
...                             contextual=True,
...                             n_contextual=10)

>>> for x, y in dataset.take(5):
...     print(x, y)
{'sine': -0.1023, 'cosine': 0.2171} 0.0
{'sine': 0.4868, 'cosine': 0.6876} 0.0
{'sine': 0.2197, 'cosine': 0.8612} 0.0
{'sine': 0.4037, 'cosine': 0.2671} 0.0
{'sine': 1.8243, 'cosine': 1.8268} 1.0


## Methods¶

take

Iterate over the k samples.

Parameters

• k (int)