Change observations according to the previous obervation value

[Dingdang]

Hi,

I have a dataset which looks like:

data have;

infile datalines;

input numbers;

datalines;

1

1

.

2

3

4

.

5

5

6

7

7

;

In case the previous obervation is not . and the present observation equals to the previous value, then i would like to set the current value to . So what I would like to have is

data want;

infile datalines;

input numbers;

datalines;

1

.

.

2

3

4

.

5

.

6

7

.

;

Can someone help me solve this problem? Many thanks in advance!

BR  Dingdang

[Haikuo · Accepted solution]

lag() or dif();

data have;

     infile datalines;

     input numbers;

     datalines;

1

1

.

2

3

4

.

5

5

6

7

7

;

data want;

     set have;

     if dif(numbers)=0 then

           numbers=.;

run;

[Ksharp]

data have;
     infile datalines;
     input numbers;
     datalines;
1
1
.
2
3
4
.
5
5
6
7
7
;
run;
data want;
 set have;
 by numbers notsorted;
 if not first.numbers then numbers=.;
 run;

 data want1;
 set have;
 by numbers notsorted;
 if numbers=lag(numbers) then numbers=.;
 run;

Xia Keshan