How to specify a variable in pandas as ordinal/categorical?

Question

I am trying to run some Machine learning algo on a dataset using scikit-learn. My dataset has some features which are like categories. Like one feature is A, wh

Answer 1

You should use the OneHotEncoder transformer with the categorical variables, and leave the ordinal variable untouched:

>>> import pandas as pd
>>> from sklearn.preprocessing import OneHotEncoder
>>> df = pd.DataFrame({'quality': [1, 2, 3], 'city': [3, 2, 1], columns=['quality', 'city']}
>>> enc = OneHotEncoder(categorical_features=[False, True])
>>> X = df.values
>>> enc.fit(X)
>>> enc.transform(X).todense()
matrix([[ 0.,  0.,  1.,  1.],
        [ 0.,  1.,  0.,  2.],
        [ 1.,  0.,  0.,  3.]])