Re: rounding off numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg23922] Re: rounding off numbers*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Fri, 16 Jun 2000 00:57:01 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <8i9p6u$2et@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In Mathematica 4.0, Windows version, the result is: N[81.3736 + (9 - 4)*0.001, 4] 81.3786 How about the following: x = 81.3736; n = 2; 10.^(-n) Round[10^n x] 81.37 Or: N[10^(-2) Round[10^2 x]] 81.37 However, your question raises the issue of why you would want to round numbers during computation. If all you really need is to round the final result of a computation, then this becomes a matter of display. So you could use, for example: NumberForm[x, 4] "81.37" (The actual result shown in the notebook is a NumberForm output cell with a label such as "Out[nn]//NumberForm=" instead of the usual "Out[nn]= ", and the quotes are NOT shown around the number 81.37.) JikaiRF at aol.com wrote: > > Dear members of MathGroup, > > I would like to report a problem rounding off numbers with Mathematica. > > Take, for example, the number 81.3736. Since I want to round it off to the > second decimal, I use the formula 81.3736 + (9-4)*0.001. And I obtain > 81.3786. > > Then, if I round off the third decimal point of the above result, 81.3786, I > > can obtain the required answer 81.37. > > In order to establish the above procedure on Mathematica, I tried the > program: > > N[81.3736 +(9-4)*0.001, 4] > > However, the result was 81.38, because the function of N is, in this > situation, designed to > round > the third decimal of 81.3786, that is,8. > > I need to round off the third decimal in the above program. > I would like to know how to program Mathematica to achieve this. > > I hope to receive useful advice from you, as I have done previously. > > Sincerely, > Fujio Takata > > P.S. My e-mail address is: JikaiRF at aol.com > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. phone 413 549-1020 (H) Univ. of Massachusetts 413 545-2859 (W) Amherst, MA 01003-4515