Path: news.mathworks.com!not-for-mail
From: "Michael Hosea" <Michael.Hosea@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Why am I unable to numerically integrate this?
Date: Fri, 23 Apr 2010 12:24:20 -0400
Organization: The MathWorks, Inc.
Lines: 30
Message-ID: <hqshjk$5e5$1@fred.mathworks.com>
References: <hqqciu$ip4$1@fred.mathworks.com>
Reply-To: "Michael Hosea" <Michael.Hosea@mathworks.com>
NNTP-Posting-Host: hoseam.dhcp.mathworks.com
X-Trace: fred.mathworks.com 1272039860 5573 144.212.115.185 (23 Apr 2010 16:24:20 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Fri, 23 Apr 2010 16:24:20 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5843
X-RFC2646: Format=Flowed; Response
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579
Xref: news.mathworks.com comp.soft-sys.matlab:629228

As already noted, you can move away from 0 slightly.  Another alternative is 
to use QUADGK instead of QUAD.  It's not as fast as QUAD on this problem, 
but it's a lot more accurate, if that matters to you, and it works "out of 
the box" here (no need to fudge the left endpoint).
--
Mike

"KC " <vistarak@gatech.edu> wrote in message 
news:hqqciu$ip4$1@fred.mathworks.com...
> Im trying to integrate this expression (k^4*exp(k))/(exp(k) - 1)^2 and 
> need a matrix of values for different limits of integration . But for some 
> reason i am getting NaN as the only answer. Any help would be much 
> appreciated.
> So far this is what I have......
>
> theta=225;
> T=[(1:1:1000)];
>
> for n=1:1000
>    x(n)=theta/T(n);
>    Q(n)=quad(@mt2p3b,0,x(n));
>    C(n)=9*R*(T(n)/theta)^3*Q(n);
> end
>
> where mt2p3b is a function handle
> function INT = mt2p3b(k)
> INT=(k.^4).*(exp(k))./(((exp(k))-1).^2);
>