Re: problems with N[]
- To: mathgroup at smc.vnet.net
- Subject: [mg38708] Re: problems with N[]
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Mon, 6 Jan 2003 03:42:59 -0500 (EST)
- References: <av94u6$sb9$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
With n <= $MachinePrecision (=16 on my machine) N[n,p] will give a machine
number
N[Pi,4]
3.14159
Precision[%]
16
Using SetPrecision we can specify precision 4
SetPrecision[Pi,4]
3.142
Precision[%]
4
However, NumberForm (which may be looked up in the Help Browser) allows us
to control the display in detail:
NumberForm[N[Pi],4]
3.142
Even though we have
Precision[%]
16
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"1.156" <rob at piovere.com> wrote in message news:av94u6$sb9$1 at smc.vnet.net...
> I'm getting a numerical output which has about 12 significant digits. I
wanted to give a printout to someone and I need only 4 significant digits
(otherwise it represents a result to precise).
>
> I thought that was what N[] was for so I put out N[result,4].
>
> For some reason I still get 12 digits displayed. I looked through he help
material and it says
> "n must lie between $MinPrecision and $MaxPrecision. $MaxPrecision can be
set to Infinity. "
> I checked and these numbers are 0 and 10^6, respectively.
>
> So, I gave up on N[] and tried Ceiling[10000*result]/10000 and damn if I
didn't get "6/625"
> for an answer.
>
> I want to display a decimal result with 4 significant digits, can anyone
tell me how to do it?
>
> Thanks.
>