Create 25-DateFunctionality.md

Author: DragonflyStats

25-DateFunctionality.md

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+Python Pandas - Date Functionality
+
+
+Extending the Time series, Date functionalities play major role in financial data analysis. While working with Date data, we will frequently come across the following −
+Generating sequence of dates
+Convert the date series to different frequencies
+Create a Range of Dates
+Using the date.range() function by specifying the periods and the frequency, we can create the date series. By default, the frequency of range is Days.
+import pandas as pd
+print pd.date_range('1/1/2011', periods=5)
+Its output is as follows −
+DatetimeIndex(['2011-01-01', '2011-01-02', '2011-01-03', '2011-01-04', '2011-01-05'],
+dtype='datetime64[ns]', freq='D')
+
+#### Change the Date Frequency
+import pandas as pd
+print pd.date_range('1/1/2011', periods=5,freq='M')
+Its output is as follows −
+DatetimeIndex(['2011-01-31', '2011-02-28', '2011-03-31', '2011-04-30', '2011-05-31'],
+dtype='datetime64[ns]', freq='M')
+bdate_range
+bdate_range() stands for business date ranges. Unlike date_range(), it excludes Saturday and Sunday.
+import pandas as pd
+print pd.date_range('1/1/2011', periods=5)
+Its output is as follows −
+DatetimeIndex(['2011-01-01', '2011-01-02', '2011-01-03', '2011-01-04', '2011-01-05'],
+dtype='datetime64[ns]', freq='D')
+Observe, after 3rd March, the date jumps to 6th march excluding 4th and 5th. Just check your calendar for the days.
+Convenience functions like date_range and bdate_range utilize a variety of frequency aliases. The default frequency for date_range is a calendar day while the default for bdate_range is a business day.
+import pandas as pd
+start = pd.datetime(2011, 1, 1)
+end = pd.datetime(2011, 1, 5)
+print pd.date_range(start, end)
+Its output is as follows −
+DatetimeIndex(['2011-01-01', '2011-01-02', '2011-01-03', '2011-01-04', '2011-01-05'],
+dtype='datetime64[ns]', freq='D')
+Offset Aliases
+A number of string aliases are given to useful common time series frequencies. We will refer to these aliases as offset aliases.
+Alias
+Description
+Alias
+Description
+B
+business day frequency
+BQS
+business quarter start frequency
+D
+calendar day frequency
+A
+annual(Year) end frequency
+W
+weekly frequency
+BA
+business year end frequency
+M
+month end frequency
+BAS
+business year start frequency
+SM
+semi-month end frequency
+BH
+business hour frequency
+BM
+business month end frequency
+H
+hourly frequency
+MS
+month start frequency
+T, min
+minutely frequency
+SMS
+SMS semi month start frequency
+S
+secondly frequency
+BMS
+business month start frequency
+L, ms
+milliseconds
+Q
+quarter end frequency
+U, us
+microseconds
+BQ
+business quarter end frequency
+N
+nanoseconds
+QS
+quarter start frequency
+