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Re: How to printout more digits?

• To: mathgroup at smc.vnet.net
• Subject: [mg46157] Re: How to printout more digits?
• From: phbrf at t-online.de (Peter Breitfeld)
• Date: Mon, 9 Feb 2004 05:54:05 -0500 (EST)
• References: <c04f0p$ggi$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Toshiyuki (Toshi) Meshii <meshii at mech.fukui-u.ac.jp> wrote:

> Hello,
> 
> I want to print out (or write to a file) outputs with more than 9 digits.
> For example, I know that
> 
> Print[ N[Pi, 9] ]
> returns
> 3.14159265
> ,which is OK.
> 
> But,
> Print[ N[6. * Pi, 9] ]
> returns
> 18.8496
> which is only 6 digits and not what I expected.
> 
> Does anybody know how to print out outputs with more than 9 digits?
> 
> In addition, I want to write the outputs in a file, such as csv files.
> If you know ideas for this, please let me know too.
> 
> -Toshi


Since Mathematica 4.0 N[number,precision] always returns only 6 Digits
for machine Precision numbers, and as you can see

Precision[6.*Pi]  gives $MachinePrecision.

To get all the wanted nine digits you can do one of the following:

N[6.0`9*Pi] --> 18.8495559
Precision[%] --> 9

or you use NumberForm:

NumberForm[6.*Pi, 9] giving 18.8495559 too, but
Precision[%] --> $MachinePrecision

NumberForm only changes the display of the number not its Precision. The
Precision of Pi and other values like Sqrt[2] is Infinity, so 
N[Pi, digits] always will show the wanted number of digits and associate
the right precision to the result:

Precision[N[Pi,9]] --> 9.
   
-- 
Gruß Peter
-- 
==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==-==
Peter Breitfeld, Bad Saulgau, Germany  -- <http://www.pBreitfeld.de>