I have a multi-label classification problem where I have more than one target and each of them is a list.

The prediction for each target can be either a list of one or more items (one or more vegetables and one or more fruits)

Features                            lables :  

  A        B       C                Vegetable                fruits
   1       3        8               [carrot, corn, carrot]   [Apricot, Cherry]
   1       3        8               [eggplant, pepper]       [Mango ]
   1       3        8               [carrot]                 [Banana, Cherry, Mango]

I was wondering what is the correct approach to take for example what could be the right model to begin with or is there a predefined models or pre-trinted model for similar problem?


2 Answers 2


If you are considering each recipe a completely different label, despite potential intersection of ingredients, you should encode your targets into distinct classes as you would normally encode labels e.g.:

>>> le = preprocessing.LabelEncoder()
>>> le.fit(["paris", "paris", "tokyo", "amsterdam"])
>>> list(le.classes_)
['amsterdam', 'paris', 'tokyo']
>>> le.transform(["tokyo", "tokyo", "paris"])
array([2, 2, 1]...)
>>> list(le.inverse_transform([2, 2, 1]))
['tokyo', 'tokyo', 'paris']

You have nested lists as class objects so to do the above you could change the type of your label column to string, in something like:

df['str_labels'] = [','.join(map(str, l)) for l in df['list_labels']]

   list_labels             str_labels
0  [carrot, corn, carrot]  carrot, corn, carrot
1  [eggplant, pepper]      eggplant, pepper

It is called multi-output, multi-label classification. Multi-output is more than 1 set of targets and within each those separate targets there can be more than 1 label.

One option would be start with traditional machine learning before trying neural networks. Scikit-learn supports this problem formation with MultiOutputClassifier.


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