Date: Tue, 29 Jun 2004 15:44:14 -0500 "Dunn, Toby" "SAS(r) Discussion" "Dunn, Toby" Re: Lag Question text/plain; charset="us-ascii"

I had thought about the retain statement which I use in the section previous to the Lag section of my paper. In fact it is a better solution than even using the Lag function in this case. However, I was trying just to use the Lag function to accomplish the same task. I guess perhaps there isn't one, possibly why I had trouble thinking of it.

Toby Dunn

-----Original Message----- From: Brian Shilling [mailto:bshilling@a-ci.com] Sent: Tuesday, June 29, 2004 3:36 PM To: Dunn, Toby Subject: RE: Lag Question

Assuming that Z is temporary to get the values from the previous records, could you use a retain statement? This works if you are going to eventually get rid of Z.

data two; set one; retain z;

if x ne . then z = x; else x = z;

run;

HTH

Brian

-----Original Message----- From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of Dunn, Toby Sent: Tuesday, June 29, 2004 4:15 PM To: SAS-L@LISTSERV.UGA.EDU Subject: Lag Question

I am working a paper and have worked myself into question.

Say you have the following dataset:

data one;

input x y \$1.;

cards;

1 a

2 a

. a

4 a

1 b

. b

. b

1 c

2 c

1 d

;

run;

and want to use the lag function to lag the value of variable (X) when ever it is missing:

Easiest I figure is the following.

data ccc;

set one;

z = lag(x);

if x = . then x = z;

run;

However, it gives a value of missing when there are two missing values of x in a row:

Obs x y z

1 1 a .

2 2 a 1

3 2 a 2

4 4 a .

5 1 b 4

6 1 b 1

7 . b .

8 1 c .

9 2 c 1

10 1 d 2

Makes since, given how the queue works when using the Lag Function. Now how would one use the Lag function and come up with value for the above missing value and a value if there were more than one missing value for x in a row?

For the life of me I can't come up with a workable solution if all I have is the LAG function.

TIA

Toby Dunn

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