Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2005
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2005

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: precisions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56003] Re: precisions
  • From: Peter Pein <petsie at arcor.de>
  • Date: Wed, 13 Apr 2005 01:10:40 -0400 (EDT)
  • References: <d3g92l$t1u$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Tun Myint Aung wrote:
> Hi All,
> 
>     I am doing a calculation involving eigenvalues and eigenvectors for
> structural mechanics. I encountered with difficulties in numerical
> calculation which is very sensitive to precisions of numerical numbers.
> I used "SetPrecision[inputdata,100] for my input data. But after I got
> eigenvalues and eigenvectors, these numbers are "MachinePrecision". I
> tried to change the precision in "Eigenvalues", but there are no options
> for that. How can I set the precision for the whole notebook?
> 
> 
> With Regards,
> Tun Myint Aung (Graduate Student)
> Civil Engineering Department
> National University of Singapore
> E1A 02-18
> E-mail: g0202015 at nus.edu.sg (or) tma at nus.edu.sg
> 
> 
> 
> 
> 
> 
Maybe you misunderstood the functionality of SetPrecision. This function
_returns_ the input set to the desired precision (as the help tells us:
 "SetPrecision[expr, p] does not modify expr itself."):

ma=Table[Random[Integer,{-10,10}],{3},{3}];
Eigenvalues[SetPrecision[N[ma],100]]
Out[12]=
{9.636466115429107974954053903389252568799915085039198891751834259486597151544\
511131541150948460400505...Rest of output left out}

-- 
Peter Pein
Berlin


  • Prev by Date: Re: local symbols inside Module
  • Next by Date: Re: Numerical Optimization involving equation solving
  • Previous by thread: Re: precisions
  • Next by thread: Re: precisions