keep just a certain number of characters

[Alrac Tom]

Dear all,

I have two variables and iI want to keep just the year of each.

(1) a long variables mdate of type "28mar1996". How can I keep just "1996"?
(2) a float variable fdate of type "1996m3".

Could anyone of you please guide so that I generate a new variable "year" where I have just 1996?

My attemp was: gen str4 year = substr(string(mdate), 1, 4) --> however here what I get instead of 1996 is 434.

Thank you in advance for any piece of advice!

[Clyde Schechter]

Stata date and time variables are complicated.

(1) a long variables mdate of type "28mar1996". How can I keep just "1996"?
(2) a float variable fdate of type "1996m3".

The best I can say is that, in Stata terminology, neither of these things exist. Point being that this description gives no clear idea what you actually have. Suggested solutions based on educated guesses of what your variables really might be have only a low probability of working.

Please post back using the -dataex- command to show actual example data from your Stata data set. Once we have that in hand, I'm pretty sure solving your problem will not be hard.

If you are running version 18, 17, 16 or a fully updated version 15.1 or 14.2, -dataex- is already part of your official Stata installation. If not, run -ssc install dataex- to get it. Either way, run -help dataex- to read the simple instructions for using it. -dataex- will save you time; it is easier and quicker than typing out tables. It includes complete information about aspects of the data that are often critical to answering your question but cannot be seen from tabular displays or screenshots. It also makes it possible for those who want to help you to create a faithful representation of your example to try out their code, which in turn makes it more likely that their answer will actually work in your data.

[Alrac Tom]

Dear Mr. Schechter,

This is what I get when typing "dataex fdate mdate"

* Example generated by -dataex-. For more info, type help dataex
clear
input long fdate float mdate
13236 434
13592 446
14326 470
15060 494
15791 518
16162 531
16526 542
16883 554
17234 566
17603 578
17969 590
18336 602
13006 427
15578 511
15935 523
16274 534
16639 546
16999 558
17367 570
17724 582
18094 594
18459 606
18821 618
19193 630
19565 642
19921 654
20284 666
20648 678
21376 702
21748 714
12929 424
13298 436
13662 448
12852 422
13584 446
13947 458
14312 470
15021 493
15755 517
16126 529
16497 542
16854 553
17220 565
17581 577
17948 589
18312 601
18676 613
19044 625
19404 637
19775 649
20146 661
20503 673
21602 709
18000 591
18396 604
14077 462
14453 474
15174 498
15544 510
15915 522
16280 534
16642 546
17013 558
17366 570
17743 582
18106 594
18471 606
18837 618
13240 435
13604 446
13970 459
14335 471
14699 482
13509 443
13879 455
18002 591
18367 603
18695 614
19099 627
19463 639
19814 651
20193 663
20557 675
21608 709
22004 722
13254 435
13692 449
13237 434
13604 446
13983 459
14334 470
14717 483
12865 422
13219 434
15421 506
15788 518
13053 428
13419 440
13786 452
14151 464
end
format %td fdate
format %tm mdate

[Clyde Schechter]

This is what I get when typing "dataex fdate mdate"

Perfect! Thank you.

gen fdate_year = year(fdate)
gen mdate_year = year(dofm(mdate))

will give you what you want.

In your example, it is the case that mdate is always just the month and year of the full date in fdate. So, if this is true in the entire data set, you don't really need two separate year variables, as they will always be the same.

Suggested reading: -help datetime-, to get an understanding of how Stata represents dates and times internally, how to control the way in which they are displayed, how to convert among different types of date/time variables, and how to create them. It's a lengthy read, and you will not remember it all on first reading. But it will give you an overview of what is going on, and you can always later refer back to the help files for unremembered syntax details when you have to actually make use of this knowledge. After some experience, the kinds of date/time variables and transformations that come up commonly in your workflow will sink in and you will become less dependent on the help file.

[Alrac Tom]

thank you very much!!!