CODEWITHSUNDEEP
sas
MaBo88
MaBo88

Reputation: 97

SAS: Creating classes by enumeration

that's probably an easy one.

I need to create a variable that is like an order but the order increases only after every second observations.

Thanks in advance!

date    order
1-1-10   1
2-1-10   1
3-1-10   2
4-1-10   2
5-1-10   3
6-1-10   3
7-1-10   4
7-1-10   4

etc

Upvotes: 1

Views: 260

Answers (2)

Stu Sztukowski
Stu Sztukowski

Reputation: 12909

You will be using two primary tools: The mod function and a sum statement. The sum statement looks like incorrect syntax, but it's a special case of retain.

_N_ is a special variable that acts as your observation counter. Every time that your data step loops from the top to the bottom (that is, from data to run), _N_ increments by one.

By using mod on _N_, we can increment a counter by one for every two observations where the result is 1. In other words, if you divide an observation count by 2 and get a remainder of 1, then add 1 to order.

For example:

_N_  _N_/2   Remainder  Operation    Value
1    1/2     1          0+1          1
2    2/2     0          N/A          1
3    3/2     1          1+1          2
4    4/2     0          N/A          2
5    5/2     1          2+1          3
6    6/2     0          N/A          3

Ultimately, we are doing an operation where we increment some value at a specific condition, carry it forward, and repeat.

How this code looks:

data want;
    set have;

    if(mod(_N_, 2) = 1) then order+1;
run;

Upvotes: 3

Petr
Petr

Reputation: 376

In data step, you can use the automatic variable _n_, e.g. ceil(_n_/2).

In SQL, monotonic() function can do the same job.

Upvotes: 0

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