Populate SAS variable by repeating values - sas

Question

I have a SAS table with a lot of missing values. This is only a simple example.
The real table is much bigger (>1000 rows) and the numbers is not the same. But what is the same is that I have a column a that have no missing numbers. Column b and c have a sequence that is shorter than the length of a.
a b c
1 1b 1000
2 2b 2000
3 3b
4
5
6
7
What I want is to fill b an c with repeating the sequences until they columns are full. The result should look like this:
a b c
1 1b 1000
2 2b 2000
3 3b 1000
4 1b 2000
5 2b 1000
6 3b 2000
7 1b 1000
I have tried to make a macro but it become to messy.

Answer 1

The hash-of-hashes solution is the most flexible here, I suspect.
data have;
infile datalines delimiter="|";
input a b $ c;
datalines;
1|1b|1000
2|2b|2000
3|3b|
4| |
5| |
6| |
7| |
;;;;
run;
%let vars=b c;
data want;
set have;
rownum = _n_;
if _n_=1 then do;
declare hash hoh(ordered:'a');
declare hiter hih('hoh');
hoh.defineKey('varname');
hoh.defineData('varname','hh');
hoh.defineDone();
declare hash hh();
do varnum = 1 to countw("&vars.");
varname = scan("&vars",varnum);
hh = _new_ hash(ordered:'a');
hh.defineKey("rownum");
hh.defineData(varname);
hh.defineDone();
hoh.replace();
end;
end;
do rc=hih.next() by 0 while (rc=0);
if strip(vvaluex(varname)) in (" ",".") then do;
num_items = hh.num_items;
rowmod = mod(_n_-1,num_items)+1;
hh.find(key:rowmod);
end;
else do;
hh.replace();
end;
rc = hih.next();
end;
keep a &Vars.;
run;
Basically, one hash is built for each variable you are using. They're each added to the hash of hashes. Then we iterate over that, and search to see if the variable requested is populated. If it is then we add it to its hash. If it isn't then we retrieve the appropriate one.

Answer 2

Assuming that you can tell how many rows to use for each variable by counting how many non-missing values are in the column then you could use this code generation technique to generate a data step that will use the POINT= option SET statements to cycle through the first Nx observations for variable X.
First get a list of the variable names;
proc transpose data=have(obs=0) out=names ;
var _all_;
run;
Then use those to generate a PROC SQL select statement to count the number of non-missing values for each variable.
filename code temp ;
data _null_;
set names end=eof ;
file code ;
if _n_=1 then put 'create table counts as select ' ;
else put ',' #;
put 'sum(not missing(' _name_ ')) as ' _name_ ;
if eof then put 'from have;' ;
run;
proc sql noprint;
%include code /source2 ;
quit;
Then transpose that so that again you have one row per variable name but this time it also has the counts in COL1.
proc transpose data=counts out=names ;
var _all_;
run;
Now use that to generate SET statements needed for a DATA step to create the output from the input.
filename code temp;
data _null_;
set names ;
file code ;
length pvar $32 ;
pvar = cats('_point',_n_);
put pvar '=mod(_n_-1,' col1 ')+1;' ;
put 'set have(keep=' _name_ ') point=' pvar ';' ;
run;
Now use the generated statements.
data want ;
set have(drop=_all_);
%include code / source2;
run;
So for your example data file with variables A, B and C and 7 total observations the LOG for the generated data step looks like this:
1229 data want ;
1230 set have(drop=_all_);
1231 %include code / source2;
NOTE: %INCLUDE (level 1) file CODE is file .../#LN00026.
1232 +_point1 =mod(_n_-1,7 )+1;
1233 +set have(keep=a ) point=_point1 ;
1234 +_point2 =mod(_n_-1,3 )+1;
1235 +set have(keep=b ) point=_point2 ;
1236 +_point3 =mod(_n_-1,2 )+1;
1237 +set have(keep=c ) point=_point3 ;
NOTE: %INCLUDE (level 1) ending.
1238 run;
NOTE: There were 7 observations read from the data set WORK.HAVE.
NOTE: The data set WORK.WANT has 7 observations and 3 variables.

Answer 3

Populate a temporary array with the values, then check the row and add the appropriate value.
Setup the data
data have;
infile datalines delimiter="|";
input a b $ c;
datalines;
1|1b|1000
2|2b|2000
3|3b|
4| |
5| |
6| |
7| |
;
Get a count of the non-null values
proc sql noprint;
select count(*)
into :n_b
from have
where b ^= "";
select count(*)
into :n_c
from have
where c ^=.;
quit;
Now populate the missing values by repeating the contents of each array.
data want;
set have;
/*Temporary Arrays*/
array bvals[&n_b] $ 32 _temporary_;
array cvals[&n_c] _temporary_;
if _n_ <= &n_b then do;
/*Populate the b array*/
bvals[_n_] = b;
end;
else do;
/*Fill the missing values*/
b = bvals[mod(_n_+&n_b-1,&n_b)+1];
end;
if _n_ <= &n_c then do;
/*populate C values array*/
cvals[_n_] = c;
end;
else do;
/*fill in the missing C values*/
c = cvals[mod(_n_+&n_c-1,&n_c)+1];
end;
run;

Answer 4

data want;
set have;
n=mod(_n_,3);
if n=0 then b='3b';
else b=cats(n,'b');
if n in (1,0) then c=1000;
else c=2000;
drop n;
run;