merge table and start with specific row

[jopo12345678]

Hello everyone,

I have this table

DATE	COUNT	CO	DE	GRADE	SUM
201401	4472	0	0	1	4476
201401	8691	0	0	2	8713
201401	8289	0	0	3	8370
201401	4	0	1	1	.
201401	22	0	1	2	.
201401	81	0	1	3	.
201401	11642	1	0	1	11651
201401	19361	1	0	2	19420
201401	15284	1	0	3	15425
201401	9	1	1	1	.
201401	59	1	1	2	.
201401	141	1	1	3	.

I want this

DATE	COUNT	CO	DE	GRADE	SUM	SUM2
201401	4472	0	0	1	4476	.
201401	8691	0	0	2	8713	.
201401	8289	0	0	3	8370	.
201401	4	0	1	1	.	4476
201401	22	0	1	2	.	8713
201401	81	0	1	3	.	8370
201401	11642	1	0	1	11651	.
201401	19361	1	0	2	19420	.
201401	15284	1	0	3	15425	.
201401	9	1	1	1	.	11651
201401	59	1	1	2	.	19420
201401	141	1	1	3	.	15425

Basecally I want make another column SUM2 same as SUM but start in row 4.

Is there anybody who can solve my problem?

[PeterClemmensen · Accepted solution]

like this?

data have;
input DATE:yymmn6. COUNT CO DE GRADE SUM ;
format DATE yymmn6.;
datalines;
201401 4472 0 0 1 4476 
201401 8691 0 0 2 8713 
201401 8289 0 0 3 8370 
201401 4 0 1 1 . 
201401 22 0 1 2 . 
201401 81 0 1 3 . 
201401 11642 1 0 1 11651 
201401 19361 1 0 2 19420 
201401 15284 1 0 3 15425 
201401 9 1 1 1 . 
201401 59 1 1 2 . 
201401 141 1 1 3 . 
;

data want;
	set have;
	SUM2 = lag3(SUM);
run;