Filtragem colaborativa

Construindo mecanismos de recomendação em Python

Rob O'Callaghan

Director of Data

Filtragem colaborativa

Encontrando usuários semelhantes

Trabalhando com dados reais

user_ratings DataFrame:

User	Book	Rating
User_233	The Great Gatsby	3.0
User_651	The Catcher in the Rye	5.0
User_131	The Lord of the Rings	3.0
User_965	The Great Gatsby	4.0
User_651	Fifty Shades of Grey	4.0
...	...	...

Fazendo pivot dos dados

user_ratings_pivot = user_ratings.pivot(index='User', 
                                        columns='Book',
                                        values='Rating')
print(user_ratings_pivot)

title     The Great Gatsby    The Catcher in the Rye    Fifty Shades of Grey
User                    
User_233               3.0                       NaN                     NaN
User_651               NaN                       5.0                     4.0
User_965               4.0                       3.0                     NaN
     ...               ...                       ...                     ...

Esparsidade dos dados

title     The Great Gatsby    The Catcher in the Rye    Fifty Shades of Grey
User                    
User_233               3.0                       NaN                     NaN
User_651               NaN                       5.0                     4.0
User_965               4.0                       3.0                     NaN
     ...               ...                       ...                     ...

print(user_ratings_pivot.dropna())

Empty DataFrame
Columns: ["The Great Gatsby", "The Catcher in the Rye", "Fifty Shades of Grey"]
Index: []

Preenchendo valores ausentes

title     The Great Gatsby    The Catcher in the Rye    Fifty Shades of Grey
User                    
User_233               3.0                       NaN                     NaN
User_651               NaN                       5.0                     4.0
User_965               4.0                       3.0                     NaN
     ...               ...                       ...                     ...

print(user_ratings_pivot["User_651"].fillna(0))

User_651               0.0                       5.0                     4.0

Preenchendo valores ausentes

avg_ratings = user_ratings_pivot.mean(axis=1)

user_ratings_pivot = user_ratings_pivot.sub(avg_ratings, axis=0)

print(user_ratings_pivot)

title     The Great Gatsby    The Catcher in the Rye    Fifty Shades of Grey
User                    
User_233               0.0                       NaN                     NaN
User_651               NaN                       0.5                    -0.5
User_965               0.5                      -0.5                     NaN
     ...               ...                       ...                     ...

Preenchendo valores ausentes

user_ratings_pivot.fillna(0)

title     The Great Gatsby    The Catcher in the Rye    Fifty Shades of Grey
User                    
User_233               0.0                       0.0                     0.0
User_651               0.0                       0.5                    -0.5
User_965               0.5                      -0.5                     0.0
     ...               ...                       ...                     ...

Vamos praticar!

Construindo mecanismos de recomendação em Python