rfOutliers function

Random forest based outlier detection

Based on random forest instance proximity measure detects training cases which are different to all other cases.

rfOutliers(model, dataset)

Arguments

• model: a random forest model returned by CoreModel
• dataset: a training set used to generate the model

Returns

For each instance from a dataset the function returns a numeric score of its strangeness to other cases.

Details

Strangeness is defined using the random forest model via a proximity matrix (see rfProximity). If the number is greater than 10, the case can be considered an outlier according to Breiman 2001.

Examples

#first create a random forest tree using CORElearn
dataset <- iris
md <- CoreModel(Species ~ ., dataset, model="rf", rfNoTrees=30, 
                maxThreads=1)
outliers <- rfOutliers(md, dataset)
plot(abs(outliers))
#for a nicer display try 
plot(md, dataset, rfGraphType="outliers")

destroyModels(md) # clean up

Author(s)

John Adeyanju Alao (as a part of his BSc thesis) and Marko Robnik-Sikonja (thesis supervisor)

See Also

CoreModel, rfProximity, rfClustering.

References

Leo Breiman: Random Forests. Machine Learning Journal, 45:5-32, 2001