CODEWITHSUNDEEP
pythondatetimepandas
WhitneyChia
WhitneyChia

Reputation: 796

time delta in pandas dataframe

Have a question regarding how to create a day count type of column in pandas. Given a list of dates, I want to be able to calculate the difference from one date to the previous date in days. Now, I can do this with simple subtraction and it will return me a timedelta object I think. What if I just want an integer number of days. Using .days seems to work with two dates but I can't get it work with a column.

Let's say I do, 

df['day_count'] = (df['INDEX_DATE'] - df['INDEX_DATE'].shift(1))

INDEX_DATE day_count 0 2009-10-06 NaT 1 2009-10-07 1 days 2 2009-10-08 1 days 3 2009-10-09 1 days 4 2009-10-12 3 days 5 2009-10-13 1 days

I get '1 days'....I only want 1.

I can use .day like this which does return me a number, but it won't work handling an entire column. 

(df['INDEX_DATE'][1] - df['INDEX_DATE'][0]).days

If I try something like this:

df['day_count'] = (df['INDEX_DATE'] - df['INDEX_DATE'].shift(1)).days

I get an error of
AttributeError: 'Series' object has no attribute 'days'

I can work around '1 days' but I'm thinking there must be a better way to do this.

Upvotes: 1

Views: 1886

Answers (1)

MaxU - stand with Ukraine
MaxU - stand with Ukraine

Reputation: 210842

Try this:

In [197]: df['day_count'] = df.INDEX_DATE.diff().dt.days

In [198]: df
Out[198]:
  INDEX_DATE  day_count
0 2009-10-06        NaN
1 2009-10-07        1.0
2 2009-10-08        1.0
3 2009-10-09        1.0
4 2009-10-12        3.0
5 2009-10-13        1.0

Upvotes: 2

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