Identifying week numbers from specific dates

[stancemcgraw]

Hello,

    I have dates that start on 3.16.19 and run through 5.31.19, and I'd like to identify the week numbers, starting with 3.16 as 1 all the way through 10. It's currently starting my weeks as 10, as in the 10th week of 2019 and since 3/16 is a Saturday, it's starting week 11 starting on 3/17. I'd like:

data have:

week10=3/16/20-3/21/20.

week11=3/17-3/23

data want:

week1:3/16-3/23

week2: 3/24-3/30

3/16 (week1)-3/23; 3/24;

week2: 3/24-3/30

3/16 (week1)-3/23; 3/24;

week2: 3/24-3/30

3/16 x3/23; 3/24;

week2: 3/24-3/30

[ballardw]

So just what code are you currently using to get "week" values?

If you know how many "weeks" something should be from a base date you should be able to get that using the INTCK and INTNX functions. I can't provide any code as you haven't said exactly when your week one should start and possibly which day of the week should be the first of the new week.

[stancemcgraw]

I was initially using the week function as:

WEEK=WEEK(date of arrival), but my date range includes 3/16/20-5/31/20, so that function outputs this:

data have:

week    date of arrival

10         3/16/2019

11         3/17/2019

11         3/22/2019

12         3/24/2019

data want:

week      date of arrival

1            3/16/2019

1            3/17/2019

1            3/22/2019

2            3/24/2019

[FreelanceReinh]

Hello @stancemcgraw,

Try this:

week=ceil((date-'15MAR2019'd)/7);

Equivalently (for your date range) you can use the INTCK function (with the shifted interval 'week.7' -- weeks starting on Saturdays), as suggested by ballardw:

week=intck('week.7','15MAR2019'd, date);

Or the WEEK function, as suggested by SASKiwi:

week=week(date-69);

The "magic" number 69 can be computed as '16MAR2019'd-nwkdom(1,1,1,2019), i.e., the difference (in days) between the first day of week 1 in your date range and the first day of week 1 of 2019 according to the WEEK function (with the default "descriptor").

[SASKiwi]

There are recognised international standards defining week numbers. The SAS WEEK function can provide some of these: 

https://documentation.sas.com/?cdcId=pgmsascdc&cdcVersion=9.4_3.5&docsetId=ds2ref&docsetTarget=n09mp...