multiclass - type_of_target returning 'multiclass-output" despite size being 1?

[rollerman111]

From the doc

'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.

but

from sklearn.utils.multiclass import type_of_target
import numpy as np
type_of_target(np.array([[1,2,3]]))
out: 'multiclass-multioutput'

Isn't this a 1 x 3 array. Both their dimension do not satisfy size > 1 (column does row doesn't)

What am I not understanding?

[ogrisel]

Isn't this a 1 x 3 array. Both their dimension do not satisfy size > 1 (column does row doesn't)

It's still a 2D array, meaning a numpy with 2 axis:

>>> y = np.array([[1,2,3]])
>>> y.ndim
2
>>> y.shape
(1, 3)

The first axis has size 1 and is expected to represent the number of samples. The second axis has size 3 and is expected to represent number of targets.

If you want to do traditional (single target) multiclass, please just pass the column you want directly as a 1D array. For instance y = np.array([1,2,3]) whould have shape (3,) and would be interpreted as an array of class labels for 3 samples.