CODEWITHSUNDEEP
python-3.xpandas
atreyi datta
atreyi datta

Reputation: 115

How sum function works with NaN element?

I have a DataFrame with some NaN values. In this DataFrame there are some rows with all NaN values. When I apply sum function on these rows, it is returning zero instead of NaN. Code is as follows:

df = pd.DataFrame(np.random.randint(10,60,size=(5,3)),
              index = ['a','c','e','f','h'],
              columns = ['One','Two','Three'])

df = df.reindex(index=['a','b','c','d','e','f','g','h'])
print(df.loc['b'].sum())

Any Suggestion?

Upvotes: 0

Views: 696

Answers (1)

ansev
ansev

Reputation: 30930

the sum function takes the NaN values ​​as 0.

if you want the result of the sum of NaN values ​​to be NaN:

df.loc['b'].sum(min_count=1)

Output:

nan

if you apply to all rows( after using reindex) you will get the following:

df.sum(axis=1,min_count=1)

a    137.0
b      NaN
c     79.0
d      NaN
e    132.0
f     95.0
g      NaN
h     81.0
dtype: float64

if you now modify a NaN value of a row:

df.at['b','One']=0
print(df)


    One   Two  Three
a  54.0  20.0   29.0
b   0.0   NaN    NaN
c  13.0  24.0   27.0
d   NaN   NaN    NaN
e  28.0  53.0   25.0
f  46.0  55.0   50.0
g   NaN   NaN    NaN
h  47.0  26.0   48.0

df.sum(axis=1,min_count=1)

a    103.0
b      0.0
c     64.0
d      NaN
e    106.0
f    151.0
g      NaN
h    121.0
dtype: float64

as you can see now the result of row b is 0

Upvotes: 1

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