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MathGroup Archive 2001

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Re: Re: Strange error message from NIntegrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28204] Re: [mg28178] Re: Strange error message from NIntegrate
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Wed, 4 Apr 2001 04:13:26 -0400 (EDT)
  • References: <9a964c$gtv@smc.vnet.net> <200104030637.CAA20042@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Use NumberForm. Example:

In[1]:=
Table[NumberForm[Exp[-3.], j], {j, 2,
 15}]
Out[1]=
{"0.05", "0.0498", "0.04979", "0.049787", "0.0497871", "0.04978707", \
"0.049787068", "0.0497870684", "0.04978706837", "0.049787068368", \
"0.0497870683679", "0.04978706836786", "0.049787068367864", \
"0.0497870683678639"}

Tomas Garza
Mexico City
----- Original Message -----
From: "Henrik Holm" <h.holm at spray.no>
To: mathgroup at smc.vnet.net
Subject: [mg28204] [mg28178] Re: Strange error message from NIntegrate


> [BobHanlon at aol.com]
>
> >  You made the power of x a list (brackets vice parenthreses).
>
> Thank you, that seems to be the problem.
>
> >  There are still problems with the numerical integration.  However, you
can
> >
> >      - approximate the answer with a finite upper limit of integration
> >      - change the number of intervals (GaussPoints)
> >      - change the method of numerical integration
> >
> >  NIntegrate[x^(3/2)*Exp[-x]*BesselI[3/2,x/2], {x,0, 1000}]
> >
> >  1.0030037040845279
> >
> >  NIntegrate[x^(3/2)*Exp[-x]*BesselI[3/2,x/2], {x,0, Infinity},
> >    GaussPoints -> 10]
> >
> >  1.0030037040849122
> >
> >  NIntegrate[x^(3/2)*Exp[-x]*BesselI[3/2,x/2], {x,0, Infinity},
> >    Method -> Trapezoidal]
> >
> >  1.0030037040847963
>
> Also. thanks for these tips.  How can I ask Mathematica to
> show the answer with more than a few digits?  (It seems that 6
> digits is standard.)
>
>
> Henrik Holm
>



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