Re: Displaying many digits
- To: mathgroup at smc.vnet.net
- Subject: [mg40961] Re: [mg40933] Displaying many digits
- From: Murray Eisenberg <murraye at attbi.com>
- Date: Fri, 25 Apr 2003 08:07:13 -0400 (EDT)
- Organization: Mathematics & Statistics, Univ. of Mass./Amherst
- References: <200304240930.FAA17480@smc.vnet.net>
- Reply-to: murray at math.umass.edu
- Sender: owner-wri-mathgroup at wolfram.com
Numbers with decimal points automatically become floating-point machine
precision, typically around 16 decimal digits on 32-bit CPUs. Then
quantities calculated from such numbers are still floating-point machine
precision. So asking for 20 digits of the 16-digit number BesselJ[1,3.]
is pointless:
Precision[BesselJ[1, 3.]]
16
By contrast, the precision of BesselJ[1, 3] is infinity (BesselJ[1,3] is
an exact quantity). So you could do:
N[BesselJ[1, 3], 20]
0.33905895852593645893
Precision[%]
20
Or, you could specify the desired precision in the second argument to
BesselJ:
BesselJ[1, 3`20]
0.3390589585259364589
Actually, that result does not have a full 20-digit precision, only 19
digits:
Precision[BesselJ[1, 3`20]]
19
To get 20-digit precision result, you'll need to supply a higher-than-20
digit precision input, for example:
BesselJ[1, 3`21]
0.33905895852593645893
Precision[%]
20
Stepan Yakovenko wrote:
>
> And what if I want to see many BesselJ's digits ?
>
> In[2]:= N[BesselJ[1,3.],20]
> Out[2]= 0.339059
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street
Amherst, MA 01375
- References:
- Displaying many digits
- From: Stepan Yakovenko <yakovenko@ngs.ru>
- Displaying many digits