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Rounding

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  • P PaulowniaK

    OK, bad example...

    123 would be 120.
    125 would be 120.
    126 would be 130.

    etc. etc.

    The point not being the number of significant digits you end up with, but the fact that the rounding is happening at 5 and 6 rather than the more usual 4 and 5.

    Almost, but not quite, entirely unlike... me...

    D Offline
    D Offline
    DaveAuld
    wrote on last edited by
    #18

    Sounds like you want to do Round Half Down + Significant then.

    Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

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    • P PaulowniaK

      My understanding of rounding to N significant figure is like this:

      1234 to 3 significant figures = 1230
      1235 to 3 significant figures = 1240
      1236 to 3 significant figures = 1240

      The trouble is, I need

      1234 to 3 significant figures = 1230
      1235 to 3 significant figures = 1230
      1236 to 3 significant figures = 1240

      The point is, rather than rounding up or down depending on whether the N+1th digit is 4 or 5, but whether it is 5 or 6.

      Almost, but not quite, entirely unlike... me...

      D Offline
      D Offline
      DaveAuld
      wrote on last edited by
      #19

      Round half down + Significant.

      Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

      P 1 Reply Last reply
      0
      • P PaulowniaK

        My understanding of rounding to N significant figure is like this:

        1234 to 3 significant figures = 1230
        1235 to 3 significant figures = 1240
        1236 to 3 significant figures = 1240

        The trouble is, I need

        1234 to 3 significant figures = 1230
        1235 to 3 significant figures = 1230
        1236 to 3 significant figures = 1240

        The point is, rather than rounding up or down depending on whether the N+1th digit is 4 or 5, but whether it is 5 or 6.

        Almost, but not quite, entirely unlike... me...

        A Offline
        A Offline
        Agent__007
        wrote on last edited by
        #20

        How about "N Significant Half-Down Rounding[^]"?

        Whether I think I can, or think I can't, I am always bloody right!

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        • P PaulowniaK

          My understanding of rounding to N significant figure is like this:

          1234 to 3 significant figures = 1230
          1235 to 3 significant figures = 1240
          1236 to 3 significant figures = 1240

          The trouble is, I need

          1234 to 3 significant figures = 1230
          1235 to 3 significant figures = 1230
          1236 to 3 significant figures = 1240

          The point is, rather than rounding up or down depending on whether the N+1th digit is 4 or 5, but whether it is 5 or 6.

          Almost, but not quite, entirely unlike... me...

          J Offline
          J Offline
          Jorgen Andersson
          wrote on last edited by
          #21

          So depending on how you want to treat negative numbers you want either "Significant digits round half down" or "Significant digits round half towards zero".

          Wrong is evil and must be defeated. - Jeff Ello[^]

          P 1 Reply Last reply
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          • P PaulowniaK

            OK, bad example...

            123 would be 120.
            125 would be 120.
            126 would be 130.

            etc. etc.

            The point not being the number of significant digits you end up with, but the fact that the rounding is happening at 5 and 6 rather than the more usual 4 and 5.

            Almost, but not quite, entirely unlike... me...

            J Offline
            J Offline
            Jorgen Andersson
            wrote on last edited by
            #22

            See my other answer, or Daves.

            Wrong is evil and must be defeated. - Jeff Ello[^]

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            • D DaveAuld

              Round half down + Significant.

              Dave Find Me On:Web|Facebook|Twitter|LinkedIn Folding Stats: Team CodeProject

              P Offline
              P Offline
              PaulowniaK
              wrote on last edited by
              #23

              Cheers. I think "round half down" is the term I needed. :thumbsup:

              Almost, but not quite, entirely unlike... me...

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              • J Jorgen Andersson

                So depending on how you want to treat negative numbers you want either "Significant digits round half down" or "Significant digits round half towards zero".

                Wrong is evil and must be defeated. - Jeff Ello[^]

                P Offline
                P Offline
                PaulowniaK
                wrote on last edited by
                #24

                All values are positive, due to the nature of the application. "Round half down" was the term I was looking for. Thanks for your help. :cool:

                Almost, but not quite, entirely unlike... me...

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                • L Lost User

                  http://en.wikipedia.org/wiki/Rounding[^] "Round half down to nearest integral multiplier power of 10"

                  Peter Wasser "The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

                  P Offline
                  P Offline
                  PaulowniaK
                  wrote on last edited by
                  #25

                  Thanks, "Round half down" was the term I was looking for. :)

                  Almost, but not quite, entirely unlike... me...

                  1 Reply Last reply
                  0
                  • S Steve Wellens

                    How's this: Round to one significant digit.

                    D Offline
                    D Offline
                    Duncan Edwards Jones
                    wrote on last edited by
                    #26

                    ...or rounding to the most significant digit. (I'd suggest that we call this "politicians rounding")

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                    • J JMK NI

                      This is standard rounding The irony is that people are so used to bankers rounding they get confused when they see ordinary rounding, but this is the kind you probably learned about in school! Disregard, I'm an idiot

                      B Offline
                      B Offline
                      BillWoodruff
                      wrote on last edited by
                      #27

                      JMK-NI wrote:

                      Disregard, I'm an idiot

                      Well, JMK-NI, don't worry too much: you are in the place for idiocy. It's kind of like a "contagious skin rash," here, on the Lounge, it breaks out in different people, and makes different people scratch in different places, while others scratch their heads. cheers, Bill

                      “I have diligently numbered the days of pure and genuine happiness which have fallen to my lot: They amount to 14.” Abd-Ar Rahman III, Caliph of Cordoba, circa 950CE.

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                      • P PaulowniaK

                        A very random question, but CPians' answers may possibly be useful for me... Is there a word or a phrase describing this:

                        1.5 gets rounded to 1.
                        1.6 gets rounded to 2.

                        150 gets rounded to 100.
                        160 gets rounded to 200.

                        and any other similar effects...

                        :confused: Any suggestions greatly appreciated.

                        Almost, but not quite, entirely unlike... me...

                        M Offline
                        M Offline
                        Michael Pauli
                        wrote on last edited by
                        #28

                        The 1.5 -> 1 is a little strange. Except for that you can use

                        double MagicFormula(double x)
                        {
                        var d = Math.Log10(x);
                        var f = Math.Pow(10.0, d);
                        var res = Math.Round(x / f, 0) * f;
                        var res2 = Math.Round(res, 0);
                        return res2;
                        }

                        Michael Pauli

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                        0
                        • P PaulowniaK

                          OK, bad example...

                          123 would be 120.
                          125 would be 120.
                          126 would be 130.

                          etc. etc.

                          The point not being the number of significant digits you end up with, but the fact that the rounding is happening at 5 and 6 rather than the more usual 4 and 5.

                          Almost, but not quite, entirely unlike... me...

                          G Offline
                          G Offline
                          Gary Wheeler
                          wrote on last edited by
                          #29

                          I think the word you are looking for is 'wrong'.

                          Software Zen: delete this;

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                          0
                          • P PaulowniaK

                            A very random question, but CPians' answers may possibly be useful for me... Is there a word or a phrase describing this:

                            1.5 gets rounded to 1.
                            1.6 gets rounded to 2.

                            150 gets rounded to 100.
                            160 gets rounded to 200.

                            and any other similar effects...

                            :confused: Any suggestions greatly appreciated.

                            Almost, but not quite, entirely unlike... me...

                            N Offline
                            N Offline
                            newton saber
                            wrote on last edited by
                            #30

                            Kind of like ceiling / floor, but that's for decimal. http://en.wikipedia.org/wiki/Floor_and_ceiling_functions[^]

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