lag function for system missing in recode

[charlene thornton]

Hi

I want to recode data. There is a date in a case followed by system missing in the cases below. I want to recode so that the system missing cells = the date above. eg

16th Aug 2009
.
.
.
.
19th August 2008
.
.
I have been trying to do this with the SYSMIS and lag function in recode - but I continue to get error messages. I am obviously a novice to writing script. Can someone please help!

[Bruce Weaver]

How is the variable holding the date formatted?  If the values are as you show below, I wonder if it is a string rather than a date format.  Please post your syntax too.

charlene thornton wrote

Hi

I want to recode data. There is a date in a case followed by system missing in the cases below. I want to recode so that the system missing cells = the date above. eg

16th Aug 2009
.
.
.
.
19th August 2008
.
.
I have been trying to do this with the SYSMIS and lag function in recode - but I continue to get error messages. I am obviously a novice to writing script. Can someone please help!

[Garry Gelade]

Hi Charlene,

Use MISSING() and LAG() as follows:

DATA LIST LIST /mydate (DATE).
BEGIN DATA
16-Aug-2009
,
,
19-Aug-2009
,
,
,
END DATA.

IF MISSING(mydate) mydate =LAG(mydate).
EXECUTE.
LIST.

    mydate

16-AUG-2009
16-AUG-2009
16-AUG-2009
19-AUG-2009
19-AUG-2009
19-AUG-2009
19-AUG-2009


Number of cases read:  7    Number of cases listed:  7

Garry Gelade
============================================================================
==

charlene thornton wrote:

>
> Hi
>
> I want to recode data. There is a date in a case followed by system
> missing in the cases below. I want to recode so that the system missing
> cells = the date above. eg
>
> 16th Aug 2009
> .
> .
> .
> .
> 19th August 2008
> .
> .
> I have been trying to do this with the SYSMIS and lag function in recode -
> but I continue to get error messages. I am obviously a novice to writing
> script. Can someone please help!
>

-----
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[Richard Ristow]

Sorry -- just want to remind folks from time to time.

At 01:13 PM 8/6/2011, Garry Gelade wrote precisely the right solution:

>IF MISSING(mydate) mydate =LAG(mydate).
>EXECUTE.
>LIST.

EXCEPT that the EXECUTE is not needed. Its only function is to force
the data to be read an extra, superfluous time -- use multiple
EXECUTEs when you have a big file, and you can drag your processing a good bit.

It isn't semantically harmless, either. Wasn't there a recent query
that posted code that didn't work because it used scratch variables,
and interposed EXECUTE statements that lost them?

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[Bruce Weaver]

Re saving processing time, a few years ago a student here was computing a bunch of new variables etc on a file with millions of records.  The COMPUTE statements were generated by pasting from the GUI, and because the default setting had not been changed, there was an EXECUTE after each one.  The job took 10 or 12 hours, IIRC.  After I removed all the unnecessary EXECUTE lines (plus a few other changes), we got it down to a few minutes.  ;-)

Richard Ristow wrote

Sorry -- just want to remind folks from time to time.

At 01:13 PM 8/6/2011, Garry Gelade wrote precisely the right solution:

>IF MISSING(mydate) mydate =LAG(mydate).
>EXECUTE.
>LIST.

EXCEPT that the EXECUTE is not needed. Its only function is to force
the data to be read an extra, superfluous time -- use multiple
EXECUTEs when you have a big file, and you can drag your processing a good bit.

It isn't semantically harmless, either. Wasn't there a recent query
that posted code that didn't work because it used scratch variables,
and interposed EXECUTE statements that lost them?

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[David Marso]

Yep!  EXECUTE sucks!  Better to do a desc or something if/when you need to pass the data.  At least you get some info from the pass.

[charlene thornton]

Thank you for answering my query - very grateful for the assistance