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Groups > comp.soft-sys.math.mathematica > #2765

Re: Rounding to a certain number of decimal places

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This seems to work:

rounded[x_?NumericQ, places_Integer] :=
 With[{iP = Length[IntegerDigits[IntegerPart[x]]]},
  PaddedForm[N[Round[x 10^places]/10^places], {iP + places, places}]]
rounded[x_, places_] := x



Andrew DeYoung wrote:

> Hi,
>
> I would like to be able to round a number to a certain, specified
> number of decimal places (not number of digits), including zeros.
> Suppose that some function f does this, and takes two arguments, the
> number to be rounded and the number of decimal places to which to
> round:  f[number, numPlaces].  Then, for example, I would like the
> following results, if possible:
>
> f[0.8168, 3] = 0.817
> f[1.8168, 3] = 1.817
> f[10.8168, 3] = 10.817
> f[100.8168, 3] = 100.817
> f[0.99, 3] = 0.990
> f[0.9, 3] = 0.900
> f[0.00572, 3] = 0.006
>
> Is there a function f (either built-in or a custom function) that can
> do this?  Mathmatica's built-in function NumberForm does not quite do
> this because the user specifies the number of digits, not the number
> of decimal places.  Also, NumberForm does not count zeros after the
> decimal point as digits, nor does it add extra zeros as needed if they
> are redundant.
>
> Am I getting into deep water here, or is there something
> straightforward that can do what I would like?
>
> I am running Mathmatica 7.  Also, I do not need to be able to do
> further computations on the output; I will be converting the output to
> a string, anyway.
>
> Thank you very much for your time.
>
> Andrew DeYoung
> Carnegie Mellon University
>

-- 
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de

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Thread

Rounding to a certain number of decimal places Andrew DeYoung <adeyoung@andrew.cmu.edu> - 2011-05-27 10:14 +0000
  Re: Rounding to a certain number of decimal places Albert Retey <awnl@gmx-topmail.de> - 2011-05-28 11:19 +0000
  Re: Rounding to a certain number of decimal places Peter Breitfeld <phbrf@t-online.de> - 2011-05-28 11:20 +0000
  Re: Rounding to a certain number of decimal places Ray Koopman <koopman@sfu.ca> - 2011-05-28 11:20 +0000
  Re: Rounding to a certain number of decimal places "Kevin J. McCann" <kjm@KevinMcCann.com> - 2011-05-28 11:21 +0000

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