I have a pandas dataframe like this:
| user_id | music_id | rating |
|---|---|---|
| A | a | 5 |
| B | a | 3 |
and I would like to create a sparse matrix from it, putting music_id as column and user_id as a row like this:
->
| a | b | |
|---|---|---|
| A | 5 | |
| B | 3 |
what would be the way to achieve it by using pandas or numpy for this task?
CodePudding user response：
If we suppose you have the following dataset as describe in your question:
d = {'user_id':['A','B'],'music_id':['a','a'],'rating':[5,3]}
df = pd.DataFrame(d)
Then you can do:
df.set_index(['user_id','music_id']).unstack(level=-1).rating
or, equivalently:
pd.pivot_table(df,values='rating',index='user_id',columns=['music_id'])