enhancement preprocessing

[franklucky001]

support OnehotEncoder, LabelEncoder, OrdinalEncoder like sklearn.

[mauricekraus]

I just tried to implement this feature, but the dataset seems to be bound to the float property, which makes it impossible to create datasets (as input) with non-numeric values. Due to the structure of the fit trait, I am unfortunately bound to the input of a dataset. Any help would be appreciated.

[YuhanLiin]

What Dataset methods are you trying to call that are bound by Float? You can access the records and targets of a Dataset via the records() and targets() methods respectively, even if the data type isn't Float. Typically those methods are all you need to implement Fit.