date-range – Tarik Billa

How to create a pandas DatetimeIndex with year as frequency?

December 12, 2023 by Tarik

Annual indexing to the beginning or end of the year Frequency is freq=’A’ for end of year frequency, ‘AS’ for start of year. Check the aliases in the documentation. eg. pd.date_range(start=pd.datetime(2000, 1, 1), periods=4, freq=’A’) returns DatetimeIndex([‘2000-12-31’, ‘2001-12-31’, ‘2002-12-31’, ‘2003-12-31′], dtype=”datetime64[ns]”, freq=’A-DEC’, tz=None) Annual indexing to the beginning of an arbitrary month If you need … Read more

How Do I Loop Through a Date Range in Reverse?

December 11, 2023 by Tarik

Try upto/downto : irb(main):003:0> sd = Date.parse(‘2010-03-01’) => #<Date: 4910513/2,0,2299161> irb(main):004:0> ed = Date.parse(‘2010-03-15’) => #<Date: 4910541/2,0,2299161> irb(main):005:0> sd.upto(ed) { |date| puts date } 2010-03-01 2010-03-02 2010-03-03 2010-03-04 2010-03-05 2010-03-06 2010-03-07 2010-03-08 2010-03-09 2010-03-10 2010-03-11 2010-03-12 2010-03-13 2010-03-14 2010-03-15 => #<Date: 4910513/2,0,2299161> irb(main):006:0> ed.downto(sd) { |date| puts date } 2010-03-15 2010-03-14 2010-03-13 2010-03-12 2010-03-11 2010-03-10 … Read more

Subsetting data.table set by date range in R

December 1, 2023 by Tarik

SQL join against date ranges?

November 29, 2023 by Tarik

You could first do a self-join on the exchange rates which are ordered by date so that you have the start and the end date of each exchange rate, without any overlap or gap in the dates (maybe add that as view to your database – in my case I’m just using a common table … Read more

Is there any kind of standard for representing date ranges?

November 22, 2023 by Tarik

ISO 8601 does have a standard for representing date ranges. To represent the start and end date using this format you would write: 2013-01-01/2013-06-31 Note how the forward slash is used as the interval designator to separate the start and end dates. See this Wikipedia page for more information.

Grep inside all files created within date range

August 23, 2023 by Tarik

This is a little different from Banthar’s solution, but it will work with versions of find that don’t support -newermt and it shows how to use the xargs command, which is a very useful tool. You can use the find command to locate files “of a certain age”. This will find all files modified between … Read more

Merge pandas dataframes where one value is between two others [duplicate]

June 28, 2023 by Tarik

As you say, this is pretty easy in SQL, so why not do it in SQL? import pandas as pd import sqlite3 #We’ll use firelynx’s tables: presidents = pd.DataFrame({“name”: [“Bush”, “Obama”, “Trump”], “president_id”:[43, 44, 45]}) terms = pd.DataFrame({‘start_date’: pd.date_range(‘2001-01-20′, periods=5, freq=’48M’), ‘end_date’: pd.date_range(‘2005-01-21′, periods=5, freq=’48M’), ‘president_id’: [43, 43, 44, 44, 45]}) war_declarations = pd.DataFrame({“date”: [datetime(2001, … Read more

PostgreSQL- Filter a date range

May 6, 2023 by Tarik

Your solution is fine. If the dates are literals, I’d prefer, though: WHERE datefield >= ‘2010-01-01 00:00:00’ AND datefield < ‘2012-01-01 00:00:00’ This performs exactly the same, but is more maintenable, because it makes clear the point of each literal “date” being a timestamp, not a date. For example, suppose sometime someone changes your query … Read more

Fetching rows added last hour

March 8, 2023 by Tarik

Make use of the DATE_SUB() and NOW() functions: select count(*) as cnt from log where date >= DATE_SUB(NOW(),INTERVAL 1 HOUR); Hope it helps you : )

Should I make a DateRange object?

February 24, 2023 by Tarik

No, you didn’t miss a general purpose class. I have a Range type in MiscUtil which you may be interested in – and it certainly makes for simple DateTime manipulation. Referring to Marc’s answer, I can’t remember whether this is a struct or a class – you’d be welcome to change it of course. It’s … Read more