DO REPEATs and DATEDIFs

[Derek Quinlan]

Hi All,

 

I'm trying to create/calculate a slew of variables that contain the number of days between consecutive dates.

 

So, basically create DateDiff_1... which equals the number of days between CONTACT_DATE_1 and CONTACT_DATE_2...

 

...create DateDiff_2... which equals the number of days between CONTACT_DATE_2 and CONTACT_DATE_3...

 

...then repeat this over and over until reaching DateDiff_1827.

 

 

I put this together....

 

DO REPEAT
  x = CONTACT_DATE_1 to CONTACT_DATE_1827
  /y = DateDiff_1 to DateDiff_1827.
COMPUTE  y = DATEDIF(x, x+1, "days").
END REPEAT.
EXECUTE.

...but it always cranks out a 0 into the cells.

 

Anybody have any thoughts where I went wrong... I'm just not seeing it!

The only thing I can think of is that in the COMPUTE  y = DATEDIF(x, x+1, "days") that it is subtracting the x date from itself instead of subtracting the next date (x+1) from x, but not sure how to correct if this is the problem.

Any help is greatly appreciated!

 

Cheers

Derek

 

 

 

 

 

 

 

--
Dr. Derek J. Quinlan
Research Project Coordinator
Psychology Lecturer
University of Western Ontario
London, Ontario


Mailing Address:
Dr. Derek J. Quinlan
The University of Western Ontario
Westminster Hall, Suite 326E
London, ON 
N6A 3K7

[Rick Oliver-3]

I think what your code is doing is adding one second to the value of date x and then calculating the date difference between x and x + one second, which in days is 0 days. You need three variable lists.

From:	Derek Quinlan <[hidden email]>
To:	[hidden email]
Date:	07/16/2010 03:26 PM
Subject:	DO REPEATs and DATEDIFs
Sent by:	"SPSSX(r) Discussion" <[hidden email]>

---

Hi All,
 
I'm trying to create/calculate a slew of variables that contain the number of days between consecutive dates.
 
So, basically create DateDiff_1... which equals the number of days between CONTACT_DATE_1 and CONTACT_DATE_2...
 
...create DateDiff_2... which equals the number of days between CONTACT_DATE_2 and CONTACT_DATE_3...
 
...then repeat this over and over until reaching DateDiff_1827.
 
 
I put this together....
 
DO REPEAT
  x = CONTACT_DATE_1 to CONTACT_DATE_1827
  /y = DateDiff_1 to DateDiff_1827.
COMPUTE  y = DATEDIF(x, x+1, "days").
END REPEAT.
EXECUTE.
...but it always cranks out a 0 into the cells.
 
Anybody have any thoughts where I went wrong... I'm just not seeing it!
The only thing I can think of is that in the COMPUTE  y = DATEDIF(x, x+1, "days") that it is subtracting the x date from itself instead of subtracting the next date (x+1) from x, but not sure how to correct if this is the problem.
Any help is greatly appreciated!
 
Cheers
Derek
 
 
 
 
 
 
 

--
Dr. Derek J. Quinlan
Research Project Coordinator
Psychology Lecturer
University of Western Ontario
London, Ontario


Mailing Address:
Dr. Derek J. Quinlan
The University of Western Ontario
Westminster Hall, Suite 326E
London, ON 
N6A 3K7

[Maguin, Eugene]

Derek,

Rick is right. If you want to use a do repeat you need three variable lists.
Like this.
By the way, you can have only 1826 differences.

DO REPEAT
  x=CONTACT_DATE_1 to CONTACT_DATE_1826/y=CONTACT_DATE_2 to
CONTACT_DATE_1827/
  z=DateDiff_1 to DateDiff_1826.
COMPUTE z=DATEDIF(x,y,"days").
END REPEAT.
EXECUTE.

Another way is to use a vector and a loop structure.

Vector x=CONTACT_DATE_1 to CONTACT_DATE_1827/DateDiff(1826).
Loop #i=1 to 1826.
COMPUTE datediff(#i)=DATEDIF(x(#i),x(#i+1),"days").
End loop.
Execute.


Gene Maguin

=====================
To manage your subscription to SPSSX-L, send a message to
[hidden email] (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD