Create dynamic SAS variable name from string - sas

Question

I have something similar to the code below, I want to create every 2 character combination within my strings and then count the occurrence of each and store in a table. I will be changing the substr statement to a do loop to iterate through the whole string. But for now I just want to get the first character pair to work;
data temp;
input cat $50.;
call symput ('regex', substr(cat,1,2));
&regex = count(cat,substr(cat,1,2));
datalines;
bvbvbsbvbvbvbvblb
dvdvdvlxvdvdgd
cdcdcdcdvdcdcdvcdcded
udvdvdvdevdvdvdvdvdvdvevdedvdv
dvdkdkdvdkdkdkudvkdkd
kdkvdkdkvdkdkvudkdkdukdvdkdkdkdv
dvkvwduvwdedkd
;
run;
Expected results;
cat bv dv cd ud kd
#### 6
#### 4
#### 8
#### 1
#### 3
#### 9
#### 1
I'd prefer not to use a proc transpose as I can't loop through the string to create all the character pairs. I'll have to manually create them and I have upto 500 characters per string, plus I would like to search for 3 and 4 string patterns.

Answer 1

You can't do what you're asking to directly. You will either have to use the macro language, or use PROC TRANSPOSE. SAS doesn't let you reference data in the way you're trying to, because it has to have already constructed the variable names and such before it reads anything in.
I'll post a different solution that uses the macro language, but I suspect TRANSPOSE is the ultimate solution here; there's no practical reason this shouldn't work with your actual problem, and if you're having trouble with that it should be possible to help - post the do loop and what you're wanting, and we can of course help. Likely you just need to put the OUTPUT in the do loop.
data temp;
input cat $50.;
cat_val = substr(cat,1,2);
_var_ = count(cat,substr(cat,1,2));
output;
datalines;
bvbvbsbvbvbvbvblb
dvdvdvlxvdvdgd
cdcdcdcdvdcdcdvcdcded
udvdvdvdevdvdvdvdvdvdvevdedvdv
dvdkdkdvdkdkdkudvkdkd
kdkvdkdkvdkdkvudkdkdukdvdkdkdkdv
dvkvwduvwdedkd
;
run;
proc transpose data=temp out=temp_T(drop=_name_);
by cat notsorted; *or by some ID variable more likely;
id cat_val;
var _var_;
run;

Answer 2

Here's a solution that uses CALL EXECUTE rather than the macro language, as I decided that was actually a better solution. I wouldn't use this in production, but it hopefully shows the concept (in particular, I would not run a PROC DATASETS for each variable separately - I would concat all the renames into one string then run that at the end. I thought this better for showing how the process might work.)
This takes advantage of timing - namely, CALL EXECUTE happens after the data step terminates, so by that point you do know what variable maps to what data point. It does have to pass the data twice in order to drop the spurious variables, though if you either know the actual number of variables you want to have, or if you're okay with the excess variables hanging around, it would be okay to skip that, and PROC DATASETS doesn't actually open the whole dataset, so it would be quite fast (even the above with five calls is quite fast).
data temp;
input cat $50.;
array _catvars[50]; *arbitrary 50 chosen here - pick one big enough for your data;
array _catvarnames[50] $ _temporary_;
cat_val = substr(cat,1,2);
_iternum = whichc(cat_val, of _catvarnames[*]);
if _iternum=0 then do;
_iternum = whichc(' ',of _catvarnames[*]);
_catvarnames[_iternum]=cat_val;
call execute('proc datasets lib=work; modify temp; rename '||vname(_catvars[_iternum])||' = '||cat_val||'; quit;');
end;
_catvars[_iternum]= count(cat,substr(cat,1,2));
if _n_=7 then do; *this needs to actually be a test for end-of-file (so add `end=eof` to the set statement or infile), but you cannot do that in DATALINES so I hardcode the example.;
call execute('data temp; set temp; drop _catvars'||put(whichc(' ',of _catvarnames[*]),2. -l)||'-_catvars50;run;');
end;
datalines;
bvbvbsbvbvbvbvblb
dvdvdvlxvdvdgd
cdcdcdcdvdcdcdvcdcded
udvdvdvdevdvdvdvdvdvdvevdedvdv
dvdkdkdvdkdkdkudvkdkd
kdkvdkdkvdkdkvudkdkdukdvdkdkdkdv
dvkvwduvwdedkd
;
run;