CODEWITHSUNDEEP
pythonpandas
jenny
jenny

Reputation: 811

How to change a DateTimeIndex in a pandas dataframe to all the same year?

I have data like this:

                   Charge 1     Charge 2
observation_date                      
1970-01-31        35.535318   0.073390
1970-02-28        27.685739   0.050302

...

2013-01-31        27.671290   0.296882
2013-02-28        26.647262   0.225714
2013-03-31        21.495699   0.362151

How do I re-index the data (the observation_date) so that all the years become 2013?

So 1970-01-31 becomes 2013-01-31, etc. I understand that there will be many times when the index will be the same.

Upvotes: 1

Views: 5030

Answers (3)

Lam
Lam

Reputation: 1

not sure if I understand your question, but you can search for year startswith 1970 and replace with 2013

eg.

new_date = re.sub('1970', '2013', observation_date)

Upvotes: -1

user3378649
user3378649

Reputation: 5354

I will write a function that update the year. I will go through a quick example here.

import pandas as pd
df = pd.DataFrame({'observation_date':["1970-01-31","1970-02-31","1970-04-31"]})
l= df.observation_date

def updateYear(x):
  n= x.split("-")
  n[0]="2013" #We replace the year data, which is the first value by 2013
  return "-".join(n)
print updateYear("1970-01-31")


df['b']= df["observation_date"].apply(lambda x:updateYear(str(x)))
print df

Output:: 

  observation_date           b
0       1970-01-31  2013-01-31
1       1970-02-31  2013-02-31
2       1970-04-31  2013-04-31

In your case: 

df= pd.read_csv(name)
df.index = df.index.apply(lambda x:updateYear(str(x)))

Upvotes: 0

unutbu
unutbu

Reputation: 879251

import pandas as pd
df = pd.read_table('data', sep='\s{2,}').set_index('observation_date')
df.index = pd.DatetimeIndex(df.index)
df.index = df.index + pd.DateOffset(year=2013)
print(df)

yields

             Charge 1  Charge 2
2013-01-31  35.535318  0.073390
2013-02-28  27.685739  0.050302
2013-01-31  27.671290  0.296882
2013-02-28  26.647262  0.225714
2013-03-31  21.495699  0.362151

Upvotes: 4

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