Re: Numerical integration and list of points

• To: mathgroup at smc.vnet.net
• Subject: [mg87654] Re: [mg87622] Numerical integration and list of points
• From: Curtis Osterhoudt <cfo at lanl.gov>
• Date: Tue, 15 Apr 2008 05:49:52 -0400 (EDT)
• Organization: LANL
• References: <200804141053.GAA13528@smc.vnet.net>

Hi, Gueromo,

It seems to work for me:

In[1]:= data = ({#1, Sin[13.4*#1]} & ) /@ Range[0, 4, 0.01];
f = Interpolation[data];
NIntegrate[f[x], {x, 0, 4}]
Integrate[f[x], {x, 0, 4}]
Integrate[Sin[a*x], x]
% /. a -> 13.4
(% /. {x -> 4}) - (% /. {x -> 0})

During evaluation of In[1]:= NIntegrate::ncvb: NIntegrate failed to \
converge to prescribed accuracy after 9 recursive bisections in x \
near {x} = {0.126211}. NIntegrate obtained 0.14786850709355207` and \
1.9590212682839143`*^-7 for the integral and error estimates. >>

Out[3]= 0.147869

Out[4]= 0.147869

Out[5]= -(Cos[a x]/a)

Out[6]= -0.0746269 Cos[13.4 x]

Out[7]= 0.147869

On Monday 14 April 2008 04:53:33 guerom00 wrote:
> Hello everyone,
>
> I have a function which I read as a list of points. I want then to
> estimate its integral. I do more or less this :
>
> data={{x1,y1},{x2,y2},...,{xN,yN}}
> f=Interpolation[data]
> NIntegrate[f[x],{x,x1,xN}]
>
> Is it the correct way ? Because Mathematica hangs without giving me an
> answer although it seems a pretty straightforward thing to do...
>
> Thanks for any suggestions.

--
==========================================================
Curtis Osterhoudt
cfo at remove_this.lanl.and_this.gov
PGP Key ID: 0x4DCA2A10
Please avoid sending me Word or PowerPoint attachments
See http://www.gnu.org/philosophy/no-word-attachments.html
==========================================================

• Prev by Date: Re: Re: A Problem with Simplify
• Next by Date: Re: Possible bug in WAV export
• Previous by thread: Numerical integration and list of points
• Next by thread: Re: Numerical integration and list of points