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 ?
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
x1andx2are both non-NaN, you wantx1?