Sklearn StratifiedKFold: ValueError: Supported target types are: ('binary', 'multiclass'). Got 'multilabel-indicator' instead

Question

Working with Sklearn stratified kfold split, and when I attempt to split using multi-class, I received on error (see below). When I tried and split using binary, it works n

Answer 1

I bumped into the same problem and found out that you can check the type of the target with this util function:

from sklearn.utils.multiclass import type_of_target
type_of_target(y)

'multilabel-indicator'

From its docstring:

• 'binary': y contains <= 2 discrete values and is 1d or a column vector.
• 'multiclass': y contains more than two discrete values, is not a sequence of sequences, and is 1d or a column vector.
• 'multiclass-multioutput': y is a 2d array that contains more than two discrete values, is not a sequence of sequences, and both dimensions are of size > 1.
• 'multilabel-indicator': y is a label indicator matrix, an array of two dimensions with at least two columns, and at most 2 unique values.

With LabelEncoder you can transform your classes into an 1d array of numbers (given your target labels are in an 1d array of categoricals/object):

from sklearn.preprocessing import LabelEncoder

label_encoder = LabelEncoder()
y = label_encoder.fit_transform(target_labels)