check all entries in a column sas and return a dummy variable sas

Question

I am new in SAS and want to check if all entries in a variable in a data set satisfy a condition (namely =1) and return just one dummy variable 0 pr one depending whether all entries in the variable are 1 or at least one is not 1. Any idea how to do it?

IF colvar = 1 THEN dummy_variable = 1 

creates another variable dummy_variable of the same size as the original variable.

Thank you

Answer 1

* Generate test data;
data have;
    colvar=0;
    colvar2=0;
    do i=1 to 20;
        colvar=round(ranuni(0));
        output;
    end;
    drop i;
run;

* Read the input dataset twice, first counting the number
* of observations and setting the dummy variables to 1 if
* the corresponding variable has the value 1 in any obser-
* vation, second outputting the result. The dummy variables
* remain unchanged during the second loop.;
data want;
    _n_=0;
    d_colvar=0;
    d_colvar2=0;
    do until (eof);
        set have end=eof;
        if colvar = 1
         then d_colvar=1;
        if colvar2 = 1
         then d_colvar2=1;
        * etc.... *;
        _n_=_n_+1;
    end;
    do _n_=1 to _n_;
        set have;
        output;
    end;
run;

Answer 2

PROC SQL is a good tool for quickly generating a summary of an arbitrarily defined condition. What exactly your condition is is not clear. I think you want the ALL_ONE value in the table the code below generates. That will be 1 when every observation has COLVAR=1. Any value that is NOT a one will cause the condition to be false (0) and so ALL_ONE will then have a value of 0 instead of 1.

You could store the result into a small table.

proc sql ;
  create table check_if_one as
     select min( colvar=1 ) as all_one
          , max( colvar=1 ) as any_one
          , max( colvar ne 1 ) as any_not_one
          , min( colvar ne 1 ) as all_not_one
     from my_table
  ;
quit;

But you could also just store the value into a macro variable that you could easily use later for some purpose.

proc sql noprint ;
   select min( colvar=1 ) into :all_one trimmed from my_table ;
quit;