[MRG] DOC fix offset value in docstring of IsolationForest
@@ -109,10 +109,12 @@ class IsolationForest(BaseBagging):
offset_ : float
Offset used to define the decision function from the raw scores.
We have the relation: decision_function = score_samples - offset_.
- The offset is set to 0.5 as in the original paper, except when a
- contamination parameter different than "auto" is provided. In that
- case, the offset is defined in such a way we obtain the expected
- number of outliers (samples with decision function < 0) in training.
+ When the contamination parameter is set to "auto", the offset is equal
+ to -0.5 as the scores of inliers are close to 0 and the scores of
+ outliers are close to -1. When a contamination parameter different
+ than "auto" is provided, the offset is defined in such a way we obtain
+ the expected number of outliers (samples with decision function < 0)
+ in training.
References
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