Isolation Forest / Autoencoder contamination parameter not effecting results?

[DrSouthmountain]

Hello,

I have have run Isolation Forest and Autoencoder methods on my own datasets. I have tried to see what impact adjusting the contamination parameter makes on the resulting ROC and precision. As far as I can see nothing changes when adjusting the contamination parameter of the classifier from 0.1 to 0.5 (or anything in between).

I have tried the same with the isolation_forest example file from the repo (keeping the randomness stable by using the random_state parameter).

Has anyone else run into the same? Or am I misunderstanding things?

[yzhao062]

Contamination does not change roc which is based on raw scores. Contamination is only change threshold in to convert raw scores to binary anomaly labels. *Yue Zhao* Assistant Professor Department of Computer Science <https://www.cs.usc.edu/> University of Southern California <https://www.usc.edu/> 1 412-877-7836 | ***@***.*** Homepage: https://viterbi-web.usc.edu/~yzhao010/

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On Wed, Apr 24, 2024 at 1:06 AM DrSouthmountain ***@***.***> wrote: Hello, I have have run Isolation Forest and Autoencoder methods on my own datasets. I have tried to see what impact adjusting the contamination parameter makes on the resulting ROC and precision. As far as I can see nothing changes when adjusting the contamination parameter of the classifier from 0.1 to 0.5 (or anything in between). I have tried the same with the isolation_forest example file from the repo (keeping the randomness stable by using the random_state parameter). Has anyone else run into the same? Or am I misunderstanding things? — Reply to this email directly, view it on GitHub <#552>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADTBN2RK6RZQD7APFT6LHATY65RWRAVCNFSM6AAAAABGWM4KZCVHI2DSMVQWIX3LMV43ERDJONRXK43TNFXW4OZWGU2TENRZHE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[DrSouthmountain]

Ah I see! Thank you for your quick reply!

[yzhao062]

Contamination does not change roc which is based on raw scores. Contamination is only change threshold in to convert raw scores to binary anomaly labels.