topic Re: Need to find the date a variable changed in New SAS User

Need to find the date a variable changed

ScotchCat — Wed, 13 Dec 2023 18:13:55 GMT

Be gentle, I'm new to SAS. I need to find the File_Date each time the Product changed. Thanks for assisting!

Data have:

File_date	Product
12/1/2023	car
12/2/2023	car
12/3/2023	car
12/4/2023	car
12/5/2023	car
12/6/2023	truck
12/7/2023	truck
12/8/2023	truck
12/9/2023	truck
12/10/2023	truck
12/11/2023	bike
12/12/2023	bike
12/13/2023	bike

Data I'd like to have:

File_date	Product
12/1/2023	car
12/6/2023	truck
12/11/2023	bike

Re: Need to find the date a variable changed

PaigeMiller — Wed, 13 Dec 2023 18:23:50 GMT

data want;
    set have;
    prev_product=lag(product);
    if product^=prev_product then output;
    drop prev_product;
run;

Re: Need to find the date a variable changed

ballardw — Wed, 13 Dec 2023 19:19:37 GMT

Assuming your data is grouped by the product and has the file date in sequence:

data want;
   set have;
   by product notsorted;
   if first.product;
run;

When you use BY in a data step SAS provides automatic variables First and Last to indicate if the observation is the first or last of the group. The Notsorted allows use of data that is grouped but not actually sorted by the BY variables.