Lag function yields no results

[Kiteulf]

lag function is having some issues with givng me the right answer:

IF lag(UTSATT) IN (2,3) THEN do; phdate3 = INTNX('day',LAG(phdate2),30); end;

My data looks like

UTSATT										PHDATE	PHDATE2	PHDATE3
1	1	20	20	.	1	1	.	.	1	20JAN10	20JAN10	.
0	.	.	.	.	.	.	.	.	.	.	.	.
0	.	.	.	.	.	.	.	.	.	.	.	.
0	.	.	.	.	.	.	.	.	.	.	.	.
0	.	.	.	.	.	.	.	.	.	.	.	.
2	3	8	20	.	3	.	1	.	1	08MAR10	08MAR10	.
0	.	.	.	.	.	.	1	.	1	19MAR10	.	.

[LinusH]

Or are you having some issues using the lag correctly...

Please share your full code.

What does the dots in your data mean, missing values?

[Kiteulf]

DATA Utsattbet2;

  SET Utsattbet;

  IF START_PHMonth > PHMonth THEN phdate = INTNX('day',datepart(etl_insert_dt),30);

  IF START_PHMonth = PHMonth AND gjenstående > 0 THEN phdate = INTNX('day',datepart(etl_insert_dt),0);

  IF START_PHmonth = PHmonth THEN DO;

  IF UTSATT IN (1,2,3) THEN phdate2 = phdate;

  End;

  IF lag(UTSATT) IN (2,3) THEN do; phdate3 = INTNX('day',LAG(phdate2),30); end;

  IF lag2(UTSATT) IN (3) THEN phdate4 =lag(phdate3)+60;

format phdate phdate2 phdate3 phdate4 test date7.;

RUN;

UTSATT	PHmonth	Day	CheckDay	PH_Date	START_PHmonth	PH1	PH2	PH3	Gjenstående	phdate	phdate2	phdate3	phdate4
1	1	20	20		1	1			1	20Jan2010	20Jan2010
0
0
0
0
2	3	8	20		3		1		1	08Mar2010	08Mar2010
0							1		1	19Mar2010
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3	1	11	20		1			1	1	11Jan2011	11Jan2011
0								1	1	21Jan2011
0								1	1	01Feb2011
0
0

[LinusH]

Is this your output data?

Please prove corresponding input data as well.

Supplying sample data in datalines/cards form will help us testing your code.

[Kiteulf]

phdate3 = INTNX('day',LAG(phdate2),30);

phdate4 = INTNX('day',LAG(phdate3),30);

This worked so, thanks anyway !

[Haikuo]

LAG function, if using conditionally, will produce "unexpected" results. "unexpected" does not mean "inconsistent" or "buggy", it merely doesn't behave the way granted or implied by its name-"lag" in a layman term. If you want to know LAG () inside-out, you need to study the SAS docs. However, if you just want it to produce the results you are expecting, as a rule of thumb, only to use it UNCONDITIONALLY. Now go back to your code:

IF lag(UTSATT) IN (2,3) THEN do; phdate3 = INTNX('day',LAG(phdate2),30); end;

IF lag2(UTSATT) IN (3) THEN phdate4 =lag(phdate3)+60;

The bold part of LAG has been used conditionally, you need to set up some temp variables to avoid that. So it can be as simple as the following:

_phdate2=lag( phdate2); _phdate3=lag(phdate3);

IF lag(UTSATT) IN (2,3) THEN do; phdate3 = INTNX('day',_phdate2,30); end;

IF lag2(UTSATT) IN (3) THEN phdate4 =_phdate3+60;

Good luck,

Haikuo

[Kiteulf]

I had to change it slightly!

	_phdate2=lag( phdate2);
	_phdate3=lag2( phdate2);
	IF lag(UTSATT) IN (2,3) THEN do;
	phdate3 = INTNX('day',_phdate2,30);
	end;
	IF lag2(UTSATT) IN (3) THEN do;
	phdate4 = INTNX('day',_phdate3,60);end;