OneHotEncoder categorical_features deprecated, how to transform specific column

Question

I need to transform the independent field from string to arithmetical notation. I am using OneHotEncoder for the transformation. My dataset has many independent columns of which some are as:

Country     |    Age       
--------------------------
Germany     |    23
Spain       |    25
Germany     |    24
Italy       |    30 

I have to encode the Country column like

0     |    1     |     2     |       3
--------------------------------------
1     |    0     |     0     |      23
0     |    1     |     0     |      25
1     |    0     |     0     |      24 
0     |    0     |     1     |      30

I succeed to get the desire transformation via using OneHotEncoder as

#Encoding the categorical data
from sklearn.preprocessing import LabelEncoder

labelencoder_X = LabelEncoder()
X[:,0] = labelencoder_X.fit_transform(X[:,0])

#we are dummy encoding as the machine learning algorithms will be
#confused with the values like Spain > Germany > France
from sklearn.preprocessing import OneHotEncoder

onehotencoder = OneHotEncoder(categorical_features=[0])
X = onehotencoder.fit_transform(X).toarray()

Now I'm getting the depreciation message to use categories='auto'. If I do so the transformation is being done for the all independent columns like country, age, salary etc.

How to achieve the transformation on the dataset 0th column only?

Answer 1

There is actually 2 warnings :

FutureWarning: The handling of integer data will change in version 0.22. Currently, the categories are determined based on the range [0, max(values)], while in the future they will be determined based on the unique values. If you want the future behaviour and silence this warning, you can specify "categories='auto'". In case you used a LabelEncoder before this OneHotEncoder to convert the categories to integers, then you can now use the OneHotEncoder directly.

and the second :

The 'categorical_features' keyword is deprecated in version 0.20 and will be removed in 0.22. You can use the ColumnTransformer instead.
"use the ColumnTransformer instead.", DeprecationWarning)

In the future, you should not define the columns in the OneHotEncoder directly, unless you want to use "categories='auto'". The first message also tells you to use OneHotEncoder directly, without the LabelEncoder first. Finally, the second message tells you to use ColumnTransformer, which is like a Pipe for columns transformations.

Here is the equivalent code for your case :

from sklearn.compose import ColumnTransformer 
ct = ColumnTransformer([("Name_Of_Your_Step", OneHotEncoder(),[0])], remainder="passthrough")) # The last arg ([0]) is the list of columns you want to transform in this step
ct.fit_transform(X)    

See also : ColumnTransformer documentation

For the above example;

Encoding Categorical data (Basically Changing Text to Numerical data i.e, Country Name)

from sklearn.preprocessing import LabelEncoder, OneHotEncoder
from sklearn.compose import ColumnTransformer
#Encode Country Column
labelencoder_X = LabelEncoder()
X[:,0] = labelencoder_X.fit_transform(X[:,0])
ct = ColumnTransformer([("Country", OneHotEncoder(), [0])], remainder = 'passthrough')
X = ct.fit_transform(X)