Date:         Thu, 31 Jan 2008 07:07:18 +0100
Reply-To:     Luca Meyer <lucameyer@vodafone.it>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Luca Meyer <lucameyer@vodafone.it>
Subject:      R: date arithmetic
Comments: To: jimjohn <azam.khan@utoronto.ca>
In-Reply-To:  <15186109.post@talk.nabble.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

Here is a SPSS 16 tested syntax:

/*** first let's have some test data **/
DATA LIST LIST /DATE1 DATE2 (2N8).
BEGIN DATA
20060827 20070717
20080130 20070104
20080130 20071105
END DATA.

/*** i first transform the numeric var into string and then compute date
variables from the string ***/
STRING #DATE1S #DATE2S (A8).
COMPUTE #DATE1S=STRING(DATE1,N8).
COMPUTE #DATE2S=STRING(DATE2,N8).
COMPUTE DATE1D = date.dmy(number(substr(ltrim(#DATE1S),7,2),f2.0),
number(substr(ltrim(#DATE1S),5,2),f2.0),
number(substr(ltrim(#DATE1S),1,4),f4.0)).
COMPUTE DATE2D = date.dmy(number(substr(ltrim(#DATE2S),7,2),f2.0),
number(substr(ltrim(#DATE2S),5,2),f2.0),
number(substr(ltrim(#DATE2S),1,4),f4.0)).
VARIABLE LEVEL DATE1D (SCALE).
FORMATS DATE1D (ADATE10).
VARIABLE WIDTH DATE1D(10).
VARIABLE LEVEL DATE2D (SCALE).
FORMATS DATE2D (ADATE10).
VARIABLE WIDTH DATE2D(10).

/*** now let's compute the difference between the new variables ***/
COMPUTE DIFFM = DATEDIF(DATE1D, DATE2D, "months").
VARIABLE LABEL DIFFM.
VARIABLE LEVEL DIFFM (SCALE).
FORMATS DIFFM (F5.0).
VARIABLE WIDTH DIFFM(5).

/*** and finally select the cases you need ***/
SELECT IF ABS(DIFFM)<8.
EXE.

HTH,
Luca

Mr. Luca MEYER
Market research, data analysis & more
www.lucameyer.com - Tel: +39.339.495.00.21


-----Messaggio originale-----
Da: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] Per conto di
jimjohn
Inviato: mercoledì 30 gennaio 2008 18.16
A: SPSSX-L@LISTSERV.UGA.EDU
Oggetto: date arithmetic

hi guys i have two numeric variables with dates in the following format
yyyymmdd, one of them is always greater than equal to the other

i want to get rid of all my records for which there is less than 8 months
difference between these two variables.

does anyone know how to do this in spss? i know of a datediff function, but
my variable has to be a string for that? is there a way to maybe just
convert them to strings and then use datediff? thanks.
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