Isolation Forest Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern) 2019 Moderator Election Q&A - Questionnaire 2019 Community Moderator Election ResultsIsolation Forest height limit absent in SkLearn implementationIsolation forest results every value -1Multivariate outlier detection with isolation forest..How to detect most effective features?

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Isolation Forest



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
2019 Moderator Election Q&A - Questionnaire
2019 Community Moderator Election ResultsIsolation Forest height limit absent in SkLearn implementationIsolation forest results every value -1Multivariate outlier detection with isolation forest..How to detect most effective features?










0












$begingroup$


Can some one please explain Isolation Forests more clearly? Everywhere I search, I find the same explanation:




Isolation Forest ‘isolates’ observations by randomly selecting a
feature and then randomly selecting a split value between the maximum
and minimum values of the selected feature.




Let's take an example to solve this:



x1 = [2, 1, 4, 6, 4, 2, 1, 2, 3, 4, 19]


How would I say that 19 is an outlier?










share|improve this question











$endgroup$
















    0












    $begingroup$


    Can some one please explain Isolation Forests more clearly? Everywhere I search, I find the same explanation:




    Isolation Forest ‘isolates’ observations by randomly selecting a
    feature and then randomly selecting a split value between the maximum
    and minimum values of the selected feature.




    Let's take an example to solve this:



    x1 = [2, 1, 4, 6, 4, 2, 1, 2, 3, 4, 19]


    How would I say that 19 is an outlier?










    share|improve this question











    $endgroup$














      0












      0








      0





      $begingroup$


      Can some one please explain Isolation Forests more clearly? Everywhere I search, I find the same explanation:




      Isolation Forest ‘isolates’ observations by randomly selecting a
      feature and then randomly selecting a split value between the maximum
      and minimum values of the selected feature.




      Let's take an example to solve this:



      x1 = [2, 1, 4, 6, 4, 2, 1, 2, 3, 4, 19]


      How would I say that 19 is an outlier?










      share|improve this question











      $endgroup$




      Can some one please explain Isolation Forests more clearly? Everywhere I search, I find the same explanation:




      Isolation Forest ‘isolates’ observations by randomly selecting a
      feature and then randomly selecting a split value between the maximum
      and minimum values of the selected feature.




      Let's take an example to solve this:



      x1 = [2, 1, 4, 6, 4, 2, 1, 2, 3, 4, 19]


      How would I say that 19 is an outlier?







      data-science-model outlier






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Apr 2 at 3:42









      Stephen Rauch

      1,52551330




      1,52551330










      asked Apr 2 at 2:49









      Shyam KishorShyam Kishor

      1




      1




















          1 Answer
          1






          active

          oldest

          votes


















          1












          $begingroup$

          Isolation Forrests can be easily thought of as a Tree based method for finding outliers. As you stated, the algorithm works by randomly selecting a feature and then partitions the data like a regular Decision Tree would. The idea is to see how much "depth" is required to get purity. Said another way, many binary decision lines would have to be drawn to isolate observations towards the middle, versus only one line may be necessary for an observation toward the outside.



          You can see this visually from the pictures below:



          enter image description here



          One of the benefits to using this method of outlier detection, relative to others, is that it has the potential to have a relatively quick outlier detection. Only a few binary lines may be necessary to detect an outlier (as shown in the second picture).



          As far as implementation, you can read about this further on the scikit-learn docs here.



          The original paper here may also be helpful.



          Source: Isolation Trees (paper)






          share|improve this answer











          $endgroup$













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            1 Answer
            1






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            active

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            active

            oldest

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            1












            $begingroup$

            Isolation Forrests can be easily thought of as a Tree based method for finding outliers. As you stated, the algorithm works by randomly selecting a feature and then partitions the data like a regular Decision Tree would. The idea is to see how much "depth" is required to get purity. Said another way, many binary decision lines would have to be drawn to isolate observations towards the middle, versus only one line may be necessary for an observation toward the outside.



            You can see this visually from the pictures below:



            enter image description here



            One of the benefits to using this method of outlier detection, relative to others, is that it has the potential to have a relatively quick outlier detection. Only a few binary lines may be necessary to detect an outlier (as shown in the second picture).



            As far as implementation, you can read about this further on the scikit-learn docs here.



            The original paper here may also be helpful.



            Source: Isolation Trees (paper)






            share|improve this answer











            $endgroup$

















              1












              $begingroup$

              Isolation Forrests can be easily thought of as a Tree based method for finding outliers. As you stated, the algorithm works by randomly selecting a feature and then partitions the data like a regular Decision Tree would. The idea is to see how much "depth" is required to get purity. Said another way, many binary decision lines would have to be drawn to isolate observations towards the middle, versus only one line may be necessary for an observation toward the outside.



              You can see this visually from the pictures below:



              enter image description here



              One of the benefits to using this method of outlier detection, relative to others, is that it has the potential to have a relatively quick outlier detection. Only a few binary lines may be necessary to detect an outlier (as shown in the second picture).



              As far as implementation, you can read about this further on the scikit-learn docs here.



              The original paper here may also be helpful.



              Source: Isolation Trees (paper)






              share|improve this answer











              $endgroup$















                1












                1








                1





                $begingroup$

                Isolation Forrests can be easily thought of as a Tree based method for finding outliers. As you stated, the algorithm works by randomly selecting a feature and then partitions the data like a regular Decision Tree would. The idea is to see how much "depth" is required to get purity. Said another way, many binary decision lines would have to be drawn to isolate observations towards the middle, versus only one line may be necessary for an observation toward the outside.



                You can see this visually from the pictures below:



                enter image description here



                One of the benefits to using this method of outlier detection, relative to others, is that it has the potential to have a relatively quick outlier detection. Only a few binary lines may be necessary to detect an outlier (as shown in the second picture).



                As far as implementation, you can read about this further on the scikit-learn docs here.



                The original paper here may also be helpful.



                Source: Isolation Trees (paper)






                share|improve this answer











                $endgroup$



                Isolation Forrests can be easily thought of as a Tree based method for finding outliers. As you stated, the algorithm works by randomly selecting a feature and then partitions the data like a regular Decision Tree would. The idea is to see how much "depth" is required to get purity. Said another way, many binary decision lines would have to be drawn to isolate observations towards the middle, versus only one line may be necessary for an observation toward the outside.



                You can see this visually from the pictures below:



                enter image description here



                One of the benefits to using this method of outlier detection, relative to others, is that it has the potential to have a relatively quick outlier detection. Only a few binary lines may be necessary to detect an outlier (as shown in the second picture).



                As far as implementation, you can read about this further on the scikit-learn docs here.



                The original paper here may also be helpful.



                Source: Isolation Trees (paper)







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Apr 2 at 3:43

























                answered Apr 2 at 3:38









                EthanEthan

                695625




                695625



























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