Path: news.mathworks.com!not-for-mail
From: "ttattl ttattl" <trantuananh2006@gmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: help me ! double integral
Date: Sun, 8 May 2011 13:48:04 +0000 (UTC)
Organization: The MathWorks, Inc.
Lines: 35
Message-ID: <iq66uk$8qd$1@newscl01ah.mathworks.com>
References: <iq50q1$j66$1@newscl01ah.mathworks.com> <iq53i5$oul$1@newscl01ah.mathworks.com> <iq5t44$i58$1@newscl01ah.mathworks.com>
Reply-To: "ttattl ttattl" <trantuananh2006@gmail.com>
NNTP-Posting-Host: www-04-blr.mathworks.com
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
X-Trace: newscl01ah.mathworks.com 1304862484 9037 172.30.248.35 (8 May 2011 13:48:04 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Sun, 8 May 2011 13:48:04 +0000 (UTC)
X-Newsreader: MATLAB Central Newsreader 2863684
Xref: news.mathworks.com comp.soft-sys.matlab:725738

"ttattl ttattl" <trantuananh2006@gmail.com> wrote in message <iq5t44$i58$1@newscl01ah.mathworks.com>...
> "Roger Stafford" wrote in message <iq53i5$oul$1@newscl01ah.mathworks.com>...
> > "ttattl ttattl" <trantuananh2006@gmail.com> wrote in message <iq50q1$j66$1@newscl01ah.mathworks.com>...
> > > I have problem how to discrete ( approximate ):
> > > 
> > > I = int(0,tn) int(0,s) f(u)duds
> > > 
> > > With tn is array o [0->1] . I divided into 1000 point 
> > - - - - - - - - - -
> >   The way you have phrased your question sounds as though you want a vector answer with a thousand elements, one for each value of tn.  If you have f(u) defined for a thousand values from 0 to 1, you could do cumtrapz on these f(u) values and then do cumtrapz on the result.
> > 
> > Roger Stafford
> ------------------------------------------------------------------------------
> thanks for your reply 
>  you right ! f(u) is de fined for a thousand values from 0 to 1 and we have it ! But you can tell me more about cumtrapz ! I not understand it ! more detail for this ! please 
> 
> Thanks 

--------------------------------

I will write more clearly what I mean
 We have t_n from 0->1 ! dt =1/1000
with every t_n We have alpha (t_n ).

Now we need double integral alpha (t_n) 

I =int (o, t_n) int(0,s) alpha(u_n) du_n ds

We input 
y=cumtrapz(alpha);
z=cumtrapz(y); 
and z is result ?? 
I not clear this ( may be it wrong )

Please help me