CODEWITHSUNDEEP
pythonpandas
kanav anand
kanav anand

Reputation: 420

How to fill NaN values from in python?

mean chart:

interval        gross(mean)
(1920, 1925]    NaN
(1925, 1930]    3.443000e+06
(1930, 1935]    4.746000e+05
(1935, 1940]    2.011249e+06

i have a huge dataframe(df) which has some Nan values in gross columns Now i want to fill those Nan values from mean chart according to respective interval.

df:

name gross interval
 k    1000   (1935, 1940]
 l     Nan   (1950, 1955]

,,,

here interval is categorical index.

Upvotes: 0

Views: 281

Answers (2)

jezrael
jezrael

Reputation: 862511

You can create new Series by map and then replace NaNs by combine_first.

Main advantage is no necessary helper column, which is necessary remove later.

df1=pd.DataFrame({'gross(mean)':[np.nan,3.443000e+06, 4.746000e+05, 2.011249e+06, 10,20,30],
                   'interval':[1922,1927,1932, 1938,1932,1938,1953]})
df1['interval'] = pd.cut(df1['interval'], bins=[1920,1925,1930,1935,1940,1945,1950,1955])
print (df1)
   gross(mean)      interval
0          NaN  (1920, 1925]
1    3443000.0  (1925, 1930]
2     474600.0  (1930, 1935]
3    2011249.0  (1935, 1940]
4         10.0  (1930, 1935]
5         20.0  (1935, 1940]
6         30.0  (1950, 1955]

df = pd.DataFrame({'name':['k','l'],
                   'gross':[1000, np.nan],
                   'interval':[1938, 1952]}, columns=['name','gross','interval'])
df['interval'] = pd.cut(df['interval'], bins=[1925,1930,1935,1940,1945,1950,1955])
print (df)
  name   gross      interval
0    k  1000.0  (1935, 1940]
1    l     NaN  (1950, 1955]

mapped = df['interval'].map(df1.set_index('interval')['gross(mean)'].to_dict())
print (mapped)
0    20.0
1    30.0
Name: interval, dtype: float64
df['gross'] = df['gross'].combine_first(mapped)
print (df)
  name   gross      interval
0    k  1000.0  (1935, 1940]
1    l    30.0  (1950, 1955]

Upvotes: 1

Clock Slave
Clock Slave

Reputation: 7967

You can add a column to the dataframe with the corresponding mean value using your mean chart (you can do a left join using pd.merge by joining on the interval column). Once you have this column, you can use - 

df['gross'].fillna(df['means'])

Upvotes: 1

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