Bioequivalence and Bioavailability Forum

To round or not to round… [Software]

posted by ElMaestro  – Belgium?, 2019-07-20 17:59  – Posting: # 20415
Views: 1,076

Hi Hötzi,

» I don’t know which kind of measurements you are comparing.

It stinks but there really is no good solution when you have to compare.
(294.1/1000) == 0.2941
[1] FALSE
(2941/10000) == 0.2941
[1] TRUE

One can read ISO standards and manuals about internal float representation (I tried andfell asleep), but at the end of the day if you need to compare you need to compare and hope for the best. Some numbers just cannot be represented accurately in binary.

If you accept an xyz fraction of error on the comparison then the solution is straightforward, like

Match = function (x,y, relative.tol)
{
 if (y<((1+relative.tol)*x))
  if (y>((1-relative.tol)*x))
    return(T)
 return(F)
}

Match(6, 6.001, 0.01)

Ugly as hell , and will not work well if you get into extreme binary representations.

Complete thread:

• Spreadsheet failures, any recent examples? ElMaestro 2019-07-18 13:43 [Software] 
  • Spreadsheet failures, any recent examples? Ohlbe 2019-07-18 14:32
    • Spreadsheet addiction Helmut 2019-07-18 16:12
      • Nasty beast Ohlbe 2019-07-18 17:30
        • Nasty beast Helmut 2019-07-18 20:26
          • Nasty beast Ohlbe 2019-07-19 11:32
            • Nasty beast ElMaestro 2019-07-19 12:32
              • Decidedly off topic Ohlbe 2019-07-19 13:38
            • OT: R limbo 101 Helmut 2019-07-19 13:00
      • Spreadsheet addiction Shuanghe 2019-07-18 18:59
        • Spreadsheet addiction Helmut 2019-07-18 20:04
          • OT: Spreadsheet addiction Shuanghe 2019-07-19 12:41
            • OT: Spreadsheet addiction Helmut 2019-07-19 14:29
              • OT: Spreadsheet addiction nobody 2019-07-19 15:53
                • OT: Spreadsheet addiction Helmut 2019-07-19 19:32
    • Spreadsheet etc. failures zizou 2019-07-20 00:18
      • As designed ☺ Helmut 2019-07-20 02:12
        • As designed ☺ ElMaestro 2019-07-20 09:08
          • To round or not to round… Helmut 2019-07-20 12:53
            • To round or not to round… ElMaestro 2019-07-20 19:59
              • floating-point math is always more complex than you think it is mittyri 2019-07-20 22:43