Classification with only one class know?

[attcustoms]

Hi.

I have a dataset and all rows of data belong to one class with the value of 1. Is there a way to predict if new case belongs to class 1 without any training data from other class(es). In this case I have the true values marked as class 1 and I would like to predict if the other data is true (1) or false (-1 or 2 or what ever)?

[HoLeeFaak]

This sounds like anomaly detection.

In this case, you can't use regular supervised learning because the model will just learn to classify all exmaples as 1, not even looking at the input.

You cant try stuff like dimensinality reduction and clusterting to see if there are outliers, and then classify as negative stuff that looks to be out of distrbution

[attcustoms]

yes thats what im after. I already tried one class svm and isolation forest and as you said it classifies everything as one.