Say I have a numpy array x = np.array([0, 1, 2]), is there a built-in function in python so that I convert element to corresponding array?
e.g.
I want to convert 0 in x to [1, 0, 0], 1 to [0, 1, 0], 2 to [0, 0, 1], and the expected output is np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]]).
I tried x[x == 0] = np.array([1, 0, 0]) but it doesn't work.
Demo:
In [38]: from sklearn.preprocessing import OneHotEncoder
In [39]: ohe = OneHotEncoder()
# modern versions of SKLearn methods don't like 1D arrays
# they expect 2D arrays, so let's make it happy ;-)
In [40]: res = ohe.fit_transform(x[:, None])
In [41]: res.A
Out[41]:
array([[ 1., 0., 0.],
[ 0., 1., 0.],
[ 0., 0., 1.]])
In [42]: res
Out[42]:
<3x3 sparse matrix of type '<class 'numpy.float64'>'
with 3 stored elements in Compressed Sparse Row format>
