topic Re: Do loop which would update a variable's value in SAS Programming

Do loop which would update a variable's value

Dinurik — Tue, 02 Apr 2019 18:07:03 GMT

Hi SAS programmers,

I am writing this do loop, but cannot really wrap my head around how to make SAS update unatt_count within a loop.

So say we have a dataset

data miss;
input miss1-miss5;
cards;
1 1 1 1 1
1 0 1 1 1
1 1 0 0 1
1 0 0 0 1
1 0 0 0 0
1 0 0 1 1
;
run;

Miss1-miss5 take a value of 1 if a subject attended the visit, and 0 if the subject did not attend.

I need to calculate variables d1-d5 for each miss1-miss5 so that for each attended visit the relative "d_" would count the number of unattended visit until the attended visit.

So far what I wrote is:

data miss2;
set miss1;
unatt_count = 0;
array idata(*) miss1-miss5;
array dd(*) d1-d5;
do i = 1 to dim(idata);
if idata(i) = 1
then dd(i) = unatt_count ;
else if idata(i) = 0
then dd(i) = unatt_count+1;
end;
run;

As expected SAS only returns values 1 and 0 for d1-d5, because unatt_count needs to be updated within a loop. I know my loop may be completely idiotic for the purpose (I am a novice to SAS programming), so I would really appreciate any advice!

Thanks!

Re: Do loop which would update a variable's value

PaigeMiller — Tue, 02 Apr 2019 18:10:23 GMT

@Dinurik wrote:

Hi SAS programmers,

I am writing this do loop, but cannot really wrap my head around how to make SAS update unatt_count within a loop.

So say we have a dataset

data miss;
input miss1-miss5;
cards;
1 1 1 1 1
1 0 1 1 1
1 1 0 0 1
1 0 0 0 1
1 0 0 0 0
1 0 0 1 1
;
run;

Miss1-miss5 take a value of 1 if a subject attended the visit, and 0 if the subject did not attend.

I need to calculate variables d1-d5 for each miss1-miss5 so that for each attended visit the relative "d_" would count the number of unattended visit until the attended visit.

Show us the desired output from this sample data.

Re: Do loop which would update a variable's value

Reeza — Tue, 02 Apr 2019 19:02:13 GMT

I think you're really looking for the first 1 in the series?

If so, WHICHN is all you need.

data miss;
input miss1-miss5;

first1 = whichn(1, of miss1-miss5);

cards;
1 1 1 1 1
1 0 1 1 1
1 1 0 0 1
1 0 0 0 1
1 0 0 0 0
1 0 0 1 1
;
run;

@Dinurik wrote:

Hi SAS programmers,

I am writing this do loop, but cannot really wrap my head around how to make SAS update unatt_count within a loop.

So say we have a dataset

data miss;
input miss1-miss5;
cards;
1 1 1 1 1
1 0 1 1 1
1 1 0 0 1
1 0 0 0 1
1 0 0 0 0
1 0 0 1 1
;
run;

Miss1-miss5 take a value of 1 if a subject attended the visit, and 0 if the subject did not attend.

I need to calculate variables d1-d5 for each miss1-miss5 so that for each attended visit the relative "d_" would count the number of unattended visit until the attended visit.

So far what I wrote is:

data miss2;
set miss1;
unatt_count = 0;
array idata(*) miss1-miss5;
array dd(*) d1-d5;
do i = 1 to dim(idata);
if idata(i) = 1
then dd(i) = unatt_count ;
else if idata(i) = 0
then dd(i) = unatt_count+1;
end;
run;

As expected SAS only returns values 1 and 0 for d1-d5, because unatt_count needs to be updated within a loop. I know my loop may be completely idiotic for the purpose (I am a novice to SAS programming), so I would really appreciate any advice!

Thanks!

Re: Do loop which would update a variable's value

Astounding — Tue, 02 Apr 2019 20:16:10 GMT

If I understand the question correctly:

data miss2;
   set miss1;
   array idata {5} miss1-miss5;
   array dd {5} d1-d5;
   d1=0;
   unatt_count=0;
   do i = 2 to dim(idata);
      unatt_count + (idata{i-1} = 0);
      if idata{i}=0 then dd{i} = unatt_count;
   end;
run;

D1 must be 0, since there can't be any unattended meetings before meeting 1.

MISS5 never gets counted in the unattended count, since it can't be used as a prior meeting. If you want to adjust the final unattended count to examine MISS5 you could add a final statement to the DATA step:

if miss5=0 then unatt_count + 1;