Isolation forest: how to deal with identical values? I am trying to develop my own implementation of isolation forest algorithm. However I don't know how to deal with points that have the same value for a given feature. To better understand the problem, consider this example:
in my dataset I have the following data: (1, 2), (3,5), (3,4)

We may suppose that after one iteration, we get the following split:

      root
     /     \
    /       \
   /         \
(1,2)    (3,4), (3,5)


Now, how am I supposed to deal with the right branch?
If (due to randomness) we decide to split according to the second feature, we should not have any problem because they are different (4 and 5). However what about if we decide to split according to the first feature (which is 3 in both cases)? Should I repeat the random feature selection until I can split the remaining data?
No need to use all the features. That is the cool part of having an ensemble. If one tree who is using a small set of data with some set of features is unable to use the feature, some other tree will use it. If the point is a true outlier, the score that is calculated later will offer the due reflection.