1. Examining model stability, an example
proc logistic data=s5238.chd5238 outest=betas;
model chd10yr(event="1")=age male sbp chol diab currsmok/
selection=forward;
run;
proc print data=betas;run;

2. Select 100 bootstrap samples
%bootsamp(indat=s5238.chd5238,outdat=outboot,reps=100,seed= );

3. Re-do analysis for each bootstrap sample
proc logistic data=outboot outest=betas noprint;
by replicate;
model chd10yr(event="1")=age male sbp chol diab currsmok/
selection=forward;
run;
proc print data=betas;run;

4. A simple summary. proc means data=betas;
var age male sbp chol diab currsmok;
run;

5. Another summary – create a string that is six characters long
Another summary – create a string that is six characters long. Each character is 0 or The first character is 1 if the first variable is in the model, 0 if it is not. The same for the other two characters.

6. %macro zeroone(indat=,outdat=models,newvar=model,vars=);
%let numvars=%sysfunc(countw(&vars));
data &outdat;
length &newvar $ &numvars..;
set &indat;
array t{&numvars} &vars;
do i=1 to &numvars;
substr(&newvar,i,1)=put((t{i} ne .),1.);
end;
run;
%mend;

7. %zeroone(indat=betas,outdat=models,newvar=model,vars= age male sbp chol diab currsmok);
proc freq data=models;
table model;
run;

8. A much more complex model
A much more complex model. Lots of interaction terms, no hierarchical model restrictions.
proc logistic data=s5238.chd5238 outest=betas descending ;
model chd10yr=age | male | chol | sbp | bmi | diab | currsmok /
selection=forward slentry=.1 hierarchy=none;/*single is default*/
run;

9. Do the complex model on the bootstrap samples.
proc logistic data=outboot outest=betas descending noprint;
by replicate;
model chd10yr=age | male | chol | sbp | bmi | diab | currsmok /
selection=forward slentry=.1 hierarchy=none;/*single is default*/
run;

10. The problem -- Lots of variable names.
%zeroone(indat=betas,outdat=models,newvar=model,vars= age male sbp chol diab currsmok);
proc contents data=betas; run;

11. Use SQL to put variables names into a macro variable
proc sql;
select name into :varnames separated by " "
from dictionary.columns
where libname="WORK" and
memname="BETAS" and
type="num" and
lowcase(name) ne "replicate" and
lowcase(name) ne "intercept" and
name ne "_LNLIKE_" ;
quit;
%let numvars=%sysfunc(countw("&varnames"));
%put &numvars;
%put &varnames;

12. Now use the zeroone macro
%zeroone(indat=betas,outdat=models1,newvar=model,vars=&varnames);
proc sql;
create table nummodels as
select distinct model
from models1 ;
select count(*) "Number of distinct models"
from nummodels
quit;