CODEWITHSUNDEEP
pythondataframe
JPC
JPC

Reputation: 5173

Merge 2 columns in pandas into one columns that have data in python

I"m not sure How to word this but I'm trying to combine 2 columns say from datafram df : 

x1  x2
NaN  3
2    2
4    2
NaN  5
8    NaN

so I would like to get result of 

X
3
2
4
5
8

I tried to use pd.merge but this won't work. pretty new to python can you guide me which function do I need in this situation ?

Upvotes: 0

Views: 983

Answers (1)

DSM
DSM

Reputation: 353059

It's not clear from your question whether you want x1 to dominate over x2 (my first guess) or whether you want the maximum of both columns (@RobStarling's guess). We can do either. To see the difference, we'll change your frame slightly:

>>> df = pd.DataFrame({'x1': {0: np.nan, 1: 2.0, 2: 4.0, 3: 1, 4: 8.0}, 'x2': {0: 3.0, 1: 2.0, 2: 2.0, 3: 5.0, 4: np.nan}})
>>> df
   x1  x2
0 NaN   3
1   2   2
2   4   2
3   1   5
4   8 NaN

[5 rows x 2 columns]

If you want x1 to win, we can use where-- we want to use x1 wherever it's not null, and x2 otherwise:

>>> df["x1"].where(~pd.isnull(df["x1"]), df["x2"])
0    3
1    2
2    4
3    1
4    8
Name: x1, dtype: float64

If you want the maximum of either:

>>> df[["x1", "x2"]].max(axis=1)
0    3
1    2
2    4
3    5
4    8
dtype: float64

Upvotes: 2

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