# anomaly_detection¶

The anomaly detection toolkit identifies data points that are different in some way from the rest of an input dataset. Each data point passed to a GraphLab Create anomaly detection model is given an anomaly score from 0 to infinity, describing how different the point is relative to the rest of the dataset. The higher the score, the more likely a point is anomalous, according to a given model. Often a threshold is chosen to make a final decision whether each point is anomalous or not; this post-processing step is left to the user.

This toolkit currently includes three models, local outlier factor for datasets with multiple features and independent observations, moving Z-score for sequential data (typically a time series), and bayesian changepoints for identifying changes in univariate data. All three of these tools apply to unsupervised problems, where the user does not have training data labeled as anonymous or typical. For cases where such training labels do exist, please consider using the graphlab.toolkits.classification toolkit. If you are unsure which model to use, the create function in the anomaly_detection namespace will pick automatically based on the schema of your dataset.

Please see the documentation for this model for more details about usage. The Anomaly Detection chapter of the User Guide provides more background on anomaly detection and walks through a more in-depth example application.

## creating an anomaly detection model¶

 create Create an anomaly detection model.

## local outlier factor¶

 local_outlier_factor.create Create a LocalOutlierFactorModel. local_outlier_factor.get_default_options Information about local outlier factor parameters. local_outlier_factor.LocalOutlierFactorModel Local outlier factor model.

## moving z-score¶

 moving_zscore.create Create a MovingZScoreModel model. moving_zscore.get_default_options Information about moving Z-score parameters. moving_zscore.MovingZScoreModel Identify anomalies in univariate series.

## bayesian changepoints¶

 bayesian_changepoints.create Create a BayesianChangepointsModel. bayesian_changepoints.get_default_options Get the default options for the toolkit _BayesianOnlineChangepoint. bayesian_changepoints.BayesianChangepointsModel Identify changepoints in a univariate time series.