Weekly number variable

[Moh Bit]

Dear All,

I am trying to create a weekly number for a sample of companies with weekly date (wdate) covering the weeks from Jan 4, 2020 to March 19, 2022 for a sample of 73 countries. For example, week number for the first week, i.e. Jan 4, 2020, is 0, for the second week Jan 11, 2020 is 2, for the third week Jan 18, 2020 is 3 and so on (please see the data below covering 4 countries). Could you please provide me with some feedback on how to to create a weekly number variable that can simply add a week number for each week across countries and years? Thank you.

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* Example generated by -dataex-. For more info, type help dataex
clear
input str56 countryname float wdate
"Argentina"  21918
"Argentina"  21925
"Argentina"  21932
"Argentina"  21939
"Argentina"  21946
"Argentina"  21953
"Argentina"  21960
"Argentina"  21967
"Argentina"  21974
"Argentina"  21981
"Argentina"  21988
"Argentina"  21995
"Argentina"  22002
"Argentina"  22009
"Argentina"  22016
"Argentina"  22023
"Argentina"  22030
"Argentina"  22037
"Argentina"  22044
"Argentina"  22051
"Argentina"  22058
"Argentina"  22065
"Argentina"  22072
"Argentina"  22079
"Argentina"  22086
"Argentina"  22093
"Argentina"  22100
"Argentina"  22107
"Argentina"  22114
"Argentina"  22121
"Argentina"  22128
"Argentina"  22135
"Argentina"  22142
"Argentina"  22149
"Argentina"  22156
"Argentina"  22163
"Argentina"  22170
"Argentina"  22177
"Argentina"  22184
"Argentina"  22191
"Argentina"  22198
"Argentina"  22205
"Argentina"  22212
"Argentina"  22219
"Argentina"  22226
"Argentina"  22233
"Argentina"  22240
"Argentina"  22247
"Argentina"  22254
"Argentina"  22261
"Argentina"  22268
"Argentina"  22275
"Argentina"  22282
"Argentina"  22289
"Argentina"  22296
"Argentina"  22303
"Argentina"  22310
"Argentina"  22317
"Argentina"  22324
"Argentina"  22331
"Argentina"  22338
"Argentina"  22345
"Argentina"  22352
"Argentina"  22359
"Argentina"  22366
"Argentina"  22373
"Argentina"  22380
"Argentina"  22387
"Argentina"  22394
"Argentina"  22401
"Argentina"  22408
"Argentina"  22415
"Argentina"  22422
"Argentina"  22429
"Argentina"  22436
"Argentina"  22443
"Argentina"  22450
"Argentina"  22457
"Argentina"  22464
"Argentina"  22471
"Argentina"  22478
"Argentina"  22485
"Argentina"  22492
"Argentina"  22499
"Argentina"  22506
"Argentina"  22513
"Argentina"  22520
"Argentina"  22527
"Argentina"  22534
"Argentina"  22541
"Argentina"  22548
"Argentina"  22555
"Argentina"  22562
"Argentina"  22569
"Argentina"  22576
"Argentina"  22583
"Argentina"  22590
"Argentina"  22597
"Argentina"  22604
"Argentina"  22611
"Argentina"  22618
"Argentina"  22625
"Argentina"  22632
"Argentina"  22639
"Argentina"  22646
"Argentina"  22653
"Argentina"  22660
"Argentina"  22667
"Argentina"  22674
"Argentina"  22681
"Argentina"  22688
"Argentina"  22695
"Argentina"  22702
"Argentina"  22709
"Argentina"  22716
"Argentina"  22723
"Australia"  21918
"Australia"  21925
"Australia"  21932
"Australia"  21939
"Australia"  21946
"Australia"  21953
"Australia"  21960
"Australia"  21967
"Australia"  21974
"Australia"  21981
"Australia"  21988
"Australia"  21995
"Australia"  22002
"Australia"  22009
"Australia"  22016
"Australia"  22023
"Australia"  22030
"Australia"  22037
"Australia"  22044
"Australia"  22051
"Australia"  22058
"Australia"  22065
"Australia"  22072
"Australia"  22079
"Australia"  22086
"Australia"  22093
"Australia"  22100
"Australia"  22107
"Australia"  22114
"Australia"  22121
"Australia"  22128
"Australia"  22135
"Australia"  22142
"Australia"  22149
"Australia"  22156
"Australia"  22163
"Australia"  22170
"Australia"  22177
"Australia"  22184
"Australia"  22191
"Australia"  22198
"Australia"  22205
"Australia"  22212
"Australia"  22219
"Australia"  22226
"Australia"  22233
"Australia"  22240
"Australia"  22247
"Australia"  22254
"Australia"  22261
"Australia"  22268
"Australia"  22275
"Australia"  22282
"Australia"  22289
"Australia"  22296
"Australia"  22303
"Australia"  22310
"Australia"  22317
"Australia"  22324
"Australia"  22331
"Australia"  22338
"Australia"  22345
"Australia"  22352
"Australia"  22359
"Australia"  22366
"Australia"  22373
"Australia"  22380
"Australia"  22387
"Australia"  22394
"Australia"  22401
"Australia"  22408
"Australia"  22415
"Australia"  22422
"Australia"  22429
"Australia"  22436
"Australia"  22443
"Australia"  22450
"Australia"  22457
"Australia"  22464
"Australia"  22471
"Australia"  22478
"Australia"  22485
"Australia"  22492
"Australia"  22499
"Australia"  22506
"Australia"  22513
"Australia"  22520
"Australia"  22527
"Australia"  22534
"Australia"  22541
"Australia"  22548
"Australia"  22555
"Australia"  22562
"Australia"  22569
"Australia"  22576
"Australia"  22583
"Australia"  22590
"Australia"  22597
"Australia"  22604
"Australia"  22611
"Australia"  22618
"Australia"  22625
"Australia"  22632
"Australia"  22639
"Australia"  22646
"Australia"  22653
"Australia"  22660
"Australia"  22667
"Australia"  22674
"Australia"  22681
"Australia"  22688
"Australia"  22695
"Australia"  22702
"Australia"  22709
"Australia"  22716
"Australia"  22723
"Austria"    21918
"Austria"    21925
"Austria"    21932
"Austria"    21939
"Austria"    21946
"Austria"    21953
"Austria"    21960
"Austria"    21967
"Austria"    21974
"Austria"    21981
"Austria"    21988
"Austria"    21995
"Austria"    22002
"Austria"    22009
"Austria"    22016
"Austria"    22023
"Austria"    22030
"Austria"    22037
"Austria"    22044
"Austria"    22051
"Austria"    22058
"Austria"    22065
"Austria"    22072
"Austria"    22079
"Austria"    22086
"Austria"    22093
"Austria"    22100
"Austria"    22107
"Austria"    22114
"Austria"    22121
"Austria"    22128
"Austria"    22135
"Austria"    22142
"Austria"    22149
"Austria"    22156
"Austria"    22163
"Austria"    22170
"Austria"    22177
"Austria"    22184
"Austria"    22191
"Austria"    22198
"Austria"    22205
"Austria"    22212
"Austria"    22219
"Austria"    22226
"Austria"    22233
"Austria"    22240
"Austria"    22247
"Austria"    22254
"Austria"    22261
"Austria"    22268
"Austria"    22275
"Austria"    22282
"Austria"    22289
"Austria"    22296
"Austria"    22303
"Austria"    22310
"Austria"    22317
"Austria"    22324
"Austria"    22331
"Austria"    22338
"Austria"    22345
"Austria"    22352
"Austria"    22359
"Austria"    22366
"Austria"    22373
"Austria"    22380
"Austria"    22387
"Austria"    22394
"Austria"    22401
"Austria"    22408
"Austria"    22415
"Austria"    22422
"Austria"    22429
"Austria"    22436
"Austria"    22443
"Austria"    22450
"Austria"    22457
"Austria"    22464
"Austria"    22471
"Austria"    22478
"Austria"    22485
"Austria"    22492
"Austria"    22499
"Austria"    22506
"Austria"    22513
"Austria"    22520
"Austria"    22527
"Austria"    22534
"Austria"    22541
"Austria"    22548
"Austria"    22555
"Austria"    22562
"Austria"    22569
"Austria"    22576
"Austria"    22583
"Austria"    22590
"Austria"    22597
"Austria"    22604
"Austria"    22611
"Austria"    22618
"Austria"    22625
"Austria"    22632
"Austria"    22639
"Austria"    22646
"Austria"    22653
"Austria"    22660
"Austria"    22667
"Austria"    22674
"Austria"    22681
"Austria"    22688
"Austria"    22695
"Austria"    22702
"Austria"    22709
"Austria"    22716
"Austria"    22723
"Bangladesh" 21918
"Bangladesh" 21925
"Bangladesh" 21932
"Bangladesh" 21939
"Bangladesh" 21946
"Bangladesh" 21953
"Bangladesh" 21960
"Bangladesh" 21967
"Bangladesh" 21974
"Bangladesh" 21981
"Bangladesh" 21988
"Bangladesh" 21995
"Bangladesh" 22002
"Bangladesh" 22009
"Bangladesh" 22016
"Bangladesh" 22023
"Bangladesh" 22030
"Bangladesh" 22037
"Bangladesh" 22044
"Bangladesh" 22051
"Bangladesh" 22058
"Bangladesh" 22065
"Bangladesh" 22072
"Bangladesh" 22079
"Bangladesh" 22086
"Bangladesh" 22093
"Bangladesh" 22100
"Bangladesh" 22107
"Bangladesh" 22114
"Bangladesh" 22121
"Bangladesh" 22128
"Bangladesh" 22135
"Bangladesh" 22142
"Bangladesh" 22149
"Bangladesh" 22156
"Bangladesh" 22163
"Bangladesh" 22170
"Bangladesh" 22177
"Bangladesh" 22184
"Bangladesh" 22191
"Bangladesh" 22198
"Bangladesh" 22205
"Bangladesh" 22212
"Bangladesh" 22219
"Bangladesh" 22226
"Bangladesh" 22233
"Bangladesh" 22240
"Bangladesh" 22247
"Bangladesh" 22254
"Bangladesh" 22261
"Bangladesh" 22268
"Bangladesh" 22275
"Bangladesh" 22282
"Bangladesh" 22289
"Bangladesh" 22296
"Bangladesh" 22303
"Bangladesh" 22310
"Bangladesh" 22317
"Bangladesh" 22324
"Bangladesh" 22331
"Bangladesh" 22338
"Bangladesh" 22345
"Bangladesh" 22352
"Bangladesh" 22359
"Bangladesh" 22366
"Bangladesh" 22373
"Bangladesh" 22380
"Bangladesh" 22387
"Bangladesh" 22394
"Bangladesh" 22401
"Bangladesh" 22408
"Bangladesh" 22415
"Bangladesh" 22422
"Bangladesh" 22429
"Bangladesh" 22436
"Bangladesh" 22443
"Bangladesh" 22450
"Bangladesh" 22457
"Bangladesh" 22464
"Bangladesh" 22471
"Bangladesh" 22478
"Bangladesh" 22485
"Bangladesh" 22492
"Bangladesh" 22499
"Bangladesh" 22506
"Bangladesh" 22513
"Bangladesh" 22520
"Bangladesh" 22527
"Bangladesh" 22534
"Bangladesh" 22541
"Bangladesh" 22548
"Bangladesh" 22555
"Bangladesh" 22562
"Bangladesh" 22569
"Bangladesh" 22576
"Bangladesh" 22583
"Bangladesh" 22590
"Bangladesh" 22597
"Bangladesh" 22604
"Bangladesh" 22611
"Bangladesh" 22618
"Bangladesh" 22625
"Bangladesh" 22632
"Bangladesh" 22639
"Bangladesh" 22646
"Bangladesh" 22653
"Bangladesh" 22660
"Bangladesh" 22667
"Bangladesh" 22674
"Bangladesh" 22681
"Bangladesh" 22688
"Bangladesh" 22695
"Bangladesh" 22702
"Bangladesh" 22709
"Bangladesh" 22716
"Bangladesh" 22723
end
format %td wdate

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[Niels Henrik Bruun]

Try:

bysort countryname (wdate): generate wnbr = (wdate - wdate[1]) / 7

[Nick Cox]

Thanks for your data example. I slimmed it down to one observation for each distinct date.

All your dates are Saturdays and 4 January 2020 was a Saturday too. So, an origin of 0 for given week numbering goes like this.

. gen wanted = (wdate - mdy(1,4,2020))/7

. su wdate dow wanted 

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
       wdate |        116     22320.5    235.4124      21918      22723
         dow |        116           6           0          6          6
      wanted |        116        57.5    33.63034          0        115

.
I fear that you may want week numbering to re-start each year, which I advise against.