Date:         Tue, 2 Nov 1999 16:24:27 -0500
Reply-To:     Howard Schreier <Howard_Schreier@ITA.DOC.GOV>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Howard Schreier <Howard_Schreier@ITA.DOC.GOV>
Subject:      Re: ROUND Fn
Content-Type: text/plain; charset=US-ASCII

This has intrigued me also.

The results from the ROUND function can be expressed as a ratio of relatively small integers. One thing I stumbled across is a way to derive the denominators:

  data;
  do i = 1 to 20000;
   * Number to round, in range -50 to 50;
   notround = 100*(ranuni(1)-0.5);
   * Interval, in set .001, .002, .003, ... 1.000;
   round_to = input(put(ranuni(2),5.3),5.3) + 0.001;
   * SAS May be wrong;
   sasround = round(notround,round_to);
   * Workaround;
   myround = round(1000*notround,1000*round_to)/1000;
   denom = floor(1/round_to);
   numer = denom * sasround;
   output;
   end;
  run;
  proc print; run;

The computed values for NUMER are all integers.

Note the truncation via FLOOR in the formula for the denominator. If ROUND_TO has
an integer reciprocal, there is no truncation, and the ROUND function is correct.