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Picking subjects with missing visit

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Occasional Contributor
Posts: 7
Accepted Solution

Picking subjects with missing visit

SAS.JPG

I have a scenario where I need to pick subject who doesn't have a corresponding repeat visit for occurance of an UNSATISFACTORY in Var1. Here in the above example subject 100 has a unsatisfactory for Year 1 visit so he comes in for a repeat visit Year 1 Repeat. But I need to find out subjects who doesn't make it to that repeat visit. I made up a Year 2 Repeat visit as greyed out here as expected record but right now missing in the database table. I can split this dataset into different datasets and somehow find out the missing repeat visit for a UNSATISFACTORY Visit but I would like to know if there is any other efficient way of find this out.

Regards

Bob


Accepted Solutions
Solution
‎10-03-2011 01:39 PM
Valued Guide
Posts: 765

Re: Picking subjects with missing visit

Hi.  I'm not sure that I understand all the possibilities, but given these criteria ...

Per subjid-

for every occurrence of Visit=10 and var1=25 there should be a corresponding Visit=30 row

for every occurrence of Visit=20 and var1=25 there should be a corresponding Visit=40 row

one idea is to use EXCEPT in PROC SQL to find observations in the 1st data set

not present in the 2nd data set (here they are the same data set).  The ALL results in

subjid 300 being listed twice in the first query (two occurrences of visit=10, var1=25

and no corresponding visit=40) ...

data x;

input subjid visit var1;

datalines;

100 10 24

100 20 25

100 30 24

200 10 25

200 30 24

300 10 25

300 10 25

300 20 25

400 20 25

400 40 24

;

run;

proc sql;


title "subjects with visit=10, var1=25 and no visit=30";

select subjid from x (where=(visit eq 10 and var1 eq 25))

except all

select subjid from x (where=(visit eq 30));

title "subjects with visit=20, var1=25 and no visit=40";

select subjid from x (where=(visit eq 20 and var1 eq 25))

except all

select subjid from x (where=(visit eq 40));


quit;

You could also merge the data set with itself BY SUBJID (given a sorted data set) ...

data a;

merge x (where=(visit eq 10 and var1 eq 25) in=a)  x (where=(visit eq 30) in=b);

if a and ^b;

by subjid;

run;


data b;

merge x (where=(visit eq 20 and var1 eq 25) in=a)  x (where=(visit eq 40) in=b);

if a and ^b;

by subjid;

run;

or a hash object (visit_ is the original value of visit in an unmatched observation) ...

data ab;

declare hash h(dataset:'x(where=(visit in (30 40))');

h.defineKey('subjid','visit');

h.defineDone();

do until(done);

   set x (where=(visit in (10 20) and var1 eq 25)) end=done;

   visit_  = visit;

   visit   = ifn(visit eq 10, 30, 40);

   if h.find() then output;

end;

stop;

drop visit;

run;

etc.


View solution in original post


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PROC Star
Posts: 7,468

Picking subjects with missing visit

Bob,

I think you'll get the best response if you state your requirements in terms of what your data state.  Are your fields for visit coded 10, 20, etc. or do they also include the (description).  Same question for var1.

If they include the descriptions, are they in mixed case as shown in your example (e.g., year and Year)?

Regardless, what is your specific requirement.  My initial guess would be that your data include both numbers and description and that you want those who have a visit=20(year 1) and var1=25(unsatisfactory) as well as having a visit=40(year 2) and a var1=25(unsatisfactory).

Occasional Contributor
Posts: 7

Picking subjects with missing visit

First, Visit and Var1 are coded only numeric. NO DESCRIPTION.

Second, Per subjid- for every occurance of Visit=10 and var1=25 there should be a corresponding Visit=30 row and

                              for every occurance of Visit=20 and var1=25 there should be a corresponding Visit=40 row present in the database table. If this above criteria is missing I want to know.



Solution
‎10-03-2011 01:39 PM
Valued Guide
Posts: 765

Re: Picking subjects with missing visit

Hi.  I'm not sure that I understand all the possibilities, but given these criteria ...

Per subjid-

for every occurrence of Visit=10 and var1=25 there should be a corresponding Visit=30 row

for every occurrence of Visit=20 and var1=25 there should be a corresponding Visit=40 row

one idea is to use EXCEPT in PROC SQL to find observations in the 1st data set

not present in the 2nd data set (here they are the same data set).  The ALL results in

subjid 300 being listed twice in the first query (two occurrences of visit=10, var1=25

and no corresponding visit=40) ...

data x;

input subjid visit var1;

datalines;

100 10 24

100 20 25

100 30 24

200 10 25

200 30 24

300 10 25

300 10 25

300 20 25

400 20 25

400 40 24

;

run;

proc sql;


title "subjects with visit=10, var1=25 and no visit=30";

select subjid from x (where=(visit eq 10 and var1 eq 25))

except all

select subjid from x (where=(visit eq 30));

title "subjects with visit=20, var1=25 and no visit=40";

select subjid from x (where=(visit eq 20 and var1 eq 25))

except all

select subjid from x (where=(visit eq 40));


quit;

You could also merge the data set with itself BY SUBJID (given a sorted data set) ...

data a;

merge x (where=(visit eq 10 and var1 eq 25) in=a)  x (where=(visit eq 30) in=b);

if a and ^b;

by subjid;

run;


data b;

merge x (where=(visit eq 20 and var1 eq 25) in=a)  x (where=(visit eq 40) in=b);

if a and ^b;

by subjid;

run;

or a hash object (visit_ is the original value of visit in an unmatched observation) ...

data ab;

declare hash h(dataset:'x(where=(visit in (30 40))');

h.defineKey('subjid','visit');

h.defineDone();

do until(done);

   set x (where=(visit in (10 20) and var1 eq 25)) end=done;

   visit_  = visit;

   visit   = ifn(visit eq 10, 30, 40);

   if h.find() then output;

end;

stop;

drop visit;

run;

etc.


Occasional Contributor
Posts: 7

Re: Picking subjects with missing visit

Mike-

Perfect. This is what I needed.

Thanks a bunch.

Bob

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