Select character variables that have all missing values

Question

I have a SAS dataset with around 3,000 variables, and I would like to get rid of the character variables for which all values are missing. I know how to do this for numeric

Answer 1

Rob and cmjohns, thank you SO MUCH for your help. Based on your solutions and an idea I had over the weekend, here is what I came up with:

%macro removeEmptyCols(origDset, outDset);
    * get the number of obs in the original dset;
    %let dsid  = %sysfunc(open(&origDset));
    %let origN = %sysfunc(attrn(&dsid, nlobs));
    %let rc    = %sysfunc(close(&dsid));

    proc transpose data= &origDset out= transpDset;
        var _all_;
    run;

    data transpDset;
        set transpDset;
        * proc transpose converted all old vars to character,
          so the . from old numeric vars no longer means 'missing';
        array oldVar_ _character_;
        do over oldVar_;
            if strip(oldVar_) = "." then oldVar_ = "";
        end;

        * each row from the old dset is now a column with varname starting with 'col';
        numMiss = cmiss(of col:);

        numCols = &origN;
    run;

    proc sql noprint;
      select _NAME_ into: varsToKeep separated by ' '
      from transpDset
      where numMiss < numCols;
    quit;

    data &outDset;
        set &origDset (keep = &varsToKeep);
    run;
%mend removeEmptyCols;

I will try all 3 ways and report back on which one is fastest...

P.S. added 23 Dec 2010 for future reference: SGF Paper 048-2010: Dropping Automatically Variables with Only Missing Values