CODEWITHSUNDEEP
pythonpandas
Nic Ross
Nic Ross

Reputation: 51

How to find the values in a dataframe and the one after it?

I have a pandas dataframe that contains river levels and rainfalls together in a DataFrame called Hourly. I would like to be able to loop through for every rainfall value and collect its river level value, plus the next river level reading. For Example:

River Level Rainfall
0.876       0.0
0.877       0.8
0.882       0.0

In this case if I was looking for the values for 0.8mm of rainfall, I would like it to return the 0.877 that is in the same row as the 0.8 and also the 0.882 in the row immediately after. I would like it to output:

0.877
0.882

Currently I have a loop that goes through and locates all the rows for a given rainfall value but cannot figure out how to get the one row after value.

Any help greatly appreciated.

Upvotes: 1

Views: 67

Answers (2)

Gius
Gius

Reputation: 514

shift is the way to go as suggested by @Andy L. If you are looking for alternatives here's another way (after Wayne suggestion):

rainfall_value = 0.8
index = data[data.Rainfall == rainfall_value].index.tolist()
index = [item for x in index for item in [x, x+1]]
result = data.iloc[index]
print(result['River Level']) 
# 1  0.877
# 2  0.882

Upvotes: 1

Andy L.
Andy L.

Reputation: 25269

Try this

s = df.Rainfall.eq(0.8)
out = df.loc[s | s.shift(), 'River Level']

Out[364]:
1    0.877
2    0.882
Name: River Level, dtype: float64

Upvotes: 2

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