Python Pandas: How To Create A Binary Matrix From Column Of Lists?

I have a Python Pandas DataFrame like the following: 1 0 a, b 1 c 2 d 3 e a, b is a string representing a list of user features How can I convert this into a bi

Solution 1:

I think you can use:

df = df.iloc[:,0].str.split(', ', expand=True)
       .stack()
       .reset_index(drop=True)
       .str.get_dummies()

print df
   a  b  c  d  e
0  1  0  0  0  0
1  0  1  0  0  0
2  0  0  1  0  0
3  0  0  0  1  0
4  0  0  0  0  1

EDITED:

print df.iloc[:,0].str.replace(' ','').str.get_dummies(sep=',')
   a  b  c  d  e
0  1  1  0  0  0
1  0  0  1  0  0
2  0  0  0  1  0
3  0  0  0  0  1

Solution 2:

I wrote a general function, with support for grouping, to do this a while back:

def sublist_uniques(data,sublist):
    categories = set()
    for d,t in data.iterrows():
        try:
            for j in t[sublist]:
                categories.add(j)
        except:
            pass
    return list(categories)

def sublists_to_dummies(f,sublist,index_key = None):
    categories = sublist_uniques(f,sublist)
    frame = pd.DataFrame(columns=categories)
    for d,i in f.iterrows():
        if type(i[sublist]) == list or np.array:
            try:
                if index_key != None:
                    key = i[index_key]
                    f =np.zeros(len(categories))
                    for j in i[sublist]:
                        f[categories.index(j)] = 1
                    if key in frame.index:
                        for j in i[sublist]:
                            frame.loc[key][j]+=1
                    else:
                        frame.loc[key]=f
                else:
                    f =np.zeros(len(categories))
                    for j in i[sublist]:
                        f[categories.index(j)] = 1
                    frame.loc[d]=f
            except:
                pass

    return frame

In [15]: a
Out[15]:
   a group     labels
0  1   new     [a, d]
1  2   old  [a, g, h]
2  3   new  [i, m, a]

In [16]: sublists_to_dummies(a,'labels')
Out[16]:
   a  d  g  i  h  m
0  1  1  0  0  0  0
1  1  0  1  0  1  0
2  1  0  0  1  0  1

In [17]: sublists_to_dummies(a,'labels','group')
Out[17]:
     a  d  g  i  h  m
new  2  1  0  1  0  1
old  1  0  1  0  1  0