Generating daily dates observations by ID

[Abdur Rub]

Hi everyone,
I am stuck and would really appreciate if someone can help me out here. I have a dataset where two variables id2 and year identifies each row uniquely. I would like to create a date variable for each id-year case that populates daily date observations. For instance, I have the dataset which looks like this

id2	year
115511	2014
115511	2015
115511	2016
115512	2014
115512	2017
115512	2013
115521	2014
115521	2015

and I would like to make it look like this, where the dots (.) show continuation of the date variable until 31-Dec

id2	year	Date
115511	2014	1-Jan-14
115511	2014	2-Jan-14
115511	2014	.
115511	2014	.
115511	2014	31-Dec-14
115511	2015	1-Jan-15
115511	2015	2-Jan-15
115511	2015	.
115511	2015	.
115511	2015	31-Dec-15

I could probably do this in excel but the dataset size limits me to open this up in Excel. Any help is much appreciated.

[Øyvind Snilsberg]

expand 400
bysort id2 year: gen double date = mdy(1,1,year) + _n - 1
drop if yofd(date)>year
format %td date

[Nick Cox]

@Øyvind Snilsberg's code is manifestly a quick if dirty way to get Stata sort out leap years. It will be correct and quicker at that than any programmer will be.

Alternatively,

clear 
input year
2015
2016 
2017 
2000
2100 
end 

gen toexpand = 365 + ((mod(year, 4) == 0 & mod(year, 100) != 0) | mod(year, 400) ==  0)  

list 

     +-----------------+
     | year   toexpand |
     |-----------------|
  1. | 2015        365 |
  2. | 2016        366 |
  3. | 2017        365 |
  4. | 2000        366 |
  5. | 2100        365 |
     +-----------------+

expand toexpand

There is documentation on such a direct solution. See https://www.stata.com/support/faqs/d...ar-indicators/

That really isn't a frequently asked or answered question that I know. Rather, once I needed to work it out, and when I had done so I knew that an answer would be safer on StataCorp's website than on any computer I had, and the company was happy to post it. The number of files or useful things lost because of computer changes or crashes or because I can't remember how I saved some stuff doesn't bear thinking about.

[Abdur Rub]

This was very useful. Thank you both,