dask.dataframe.Series.first

Series.first(offset)

Select initial periods of time series data based on a date offset.

This docstring was copied from pandas.core.frame.DataFrame.first.

Some inconsistencies with the Dask version may exist.

When having a DataFrame with dates as index, this function can select the first few rows based on a date offset.

Parameters
offsetstr, DateOffset or dateutil.relativedelta

The offset length of the data that will be selected. For instance, ‘1M’ will display all the rows having their index within the first month.

Returns
Series or DataFrame

A subset of the caller.

Raises
TypeError

If the index is not a DatetimeIndex

See also

last

Select final periods of time series based on a date offset.

at_time

Select values at a particular time of the day.

between_time

Select values between particular times of the day.

Examples

>>> i = pd.date_range('2018-04-09', periods=4, freq='2D')  
>>> ts = pd.DataFrame({'A': [1, 2, 3, 4]}, index=i)  
>>> ts  
            A
2018-04-09  1
2018-04-11  2
2018-04-13  3
2018-04-15  4

Get the rows for the first 3 days:

>>> ts.first('3D')  
            A
2018-04-09  1
2018-04-11  2

Notice the data for 3 first calendar days were returned, not the first 3 days observed in the dataset, and therefore data for 2018-04-13 was not returned.