topic Please correct my understanding of the datastep process in the code? in SAS Programming

Please correct my understanding of the datastep process in the code?

CharlotteCain — Sun, 21 Dec 2014 12:34:33 GMT

Hey SAS Experts,

Please correct my understanding of the PDV in the below code:

The program runs perfectly fine.

data have;

input id $ date value holddate holdvalue lastdate lastvalue;

informat date holddate lastdate ddmmyy10.;

format date holddate lastdate ddmmyy10.;

datalines;

A 7/10/2014 11840 7/10/2014 11840 4/10/2014 15280

;

data need;

set have;

if date ne lastdate+1 then do date=lastdate+1 to holddate-1;

value=lastvalue;

output;

end;

putlog _all_; /* I tried looking at the PDV details, still haven't understood though */

value=holdvalue;

lastdate=date;

lastvalue=value;

output;

run;

Where does it say in the program after the conditional do loop to get the date value to 7/10/2014 as it outputs exactly what is needed?I.e My point is after the execution of the do loop, shouldn't date have the value of 6/10/2014 in the PDV? how did it correctly change to 7/10/2014 after i.e during the execution of 2nd output statement?

I know I am breaking my head for something simple, but your quick help would mean a lot to me.

Many thanks,

Charlotte

Re: Please correct my understanding of the datastep process in the code?

Ksharp — Sun, 21 Dec 2014 13:45:31 GMT

Very Interesting Question.

do date=lastdate+1 to holddate-1; <=> do date=lastdate+1 to holddate-1 by 1;

Maybe date will add one automatically when it reach holddate-1 . therefore date actually would be holddate-1+1 = holddate .

Anyway it is good know this about SAS syntax.

Xia Keshan

Re: Please correct my understanding of the datastep process in the code?

data_null__ — Sun, 21 Dec 2014 14:50:58 GMT

I think this illustrates how it works more clearly than your example. The index is incremented and then compared to stop leaving the value of I at 4 when the loop is finished. You could use UNTIL to make it stop and leave the index eq to stop..

data _null_; 
   do i = 1 to 3; 
      put i=;
      end; 
   put i=;
   run; 

i=1
i=2
i=3
i=4

data _null_; 
   do i = 1 to 3 until(i eq 3);
      put i=;
      end; 
   put i=;
   run; 

i=1
i=2
i=3
i=3