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: <email@example.com>
- Sender: owner-wri-mathgroup at wolfram.com
In Mathematica 4.0, Windows version, the result is:
N[81.3736 + (9 - 4)*0.001, 4]
How about the following:
x = 81.3736; n = 2;
10.^(-n) Round[10^n x]
N[10^(-2) Round[10^2 x]]
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:
(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
> 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
> 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
> 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.
> 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
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