Deleting observations after a particular date.

[DY Kim]

I want to delete all observations in a panel dataset after 2021-01 through 2021-03. Would you please tell me how I can delete them? Thank you.

. tab date

date | Freq. Percent Cum.
----------------------+-----------------------------------
2017-01 | 2,430 1.97 1.97
2017-02 | 2,430 1.97 3.95
………

2020-11 | 2,430 1.97 92.75
2020-12 | 2,430 1.97 94.73
2021-01 | 2,165 1.76 96.48
2021-02 | 2,165 1.76 98.24
2021-03 | 2,165 1.76 100.00
----------------------+-----------------------------------
Total | 123,135 100.00

[Fei Wang]

Could you please show us your example dataset using command -dataex-? We won't be able to give precise suggestion unless we know the storage type of "date".

[DY Kim]

Please see below for the variable information. I am not sure why "2021-02" and "2021-03" do not sure in the list below. Thank you for the help.

----------------------- copy starting from the next line -----------------------

* Example generated by -dataex-. To install: ssc install dataex
clear
input str21 date
"2017-01"
"2017-02"
-----

"2020-11"
"2020-12"
"2021-01"
end

------------------ copy up to and including the previous line ------------------

Listed 100 out of 123135 observations
Use the count() option to list more

[Nick Cox]

Your dates are clear but not yet fit for any serious Stata purpose. I am alarmed on your behalf that date is shown as str21 which suggests that garbage has been imported in some observations.

list date if strlen(date) > 7

will flush out unsuitable values. Otherwise this shows some technique

* Example generated by -dataex-. To install: ssc install dataex
clear
input str21 date
"2017-01"
"2017-02"
"2020-11"
"2020-12"
"2021-01"
end

gen mdate = monthly(date, "YM")
format mdate %tm 

list

Now you can just

drop if mdate >= ym(2021, 1)