Thanks a lot :) Feeling embarassed ! Alex --- On Mon, 1/10/11, Petr PIKAL <[email protected]> wrote:
> From: Petr PIKAL <[email protected]> > Subject: Odp: [R] Integration in R > To: "Alaios" <[email protected]> > Cc: [email protected] > Date: Monday, January 10, 2011, 2:45 PM > Hi > > [email protected] > napsal dne 10.01.2011 15:12:33: > > > Dear all, > > > > It has been ages since I studied > integration in college. Right now I > > try to recover all this kind of knowledge and then try > to understand how > > integration works. > > > > > > > > Thus I am doing some first 'experiments' and I would > like to request > your help > > and comments. > > > > > > > > I have the function: > > > > > > > > p2<-function(x){0.5*(3*x^2-1)} > > > > # I found the square of p2 by using some pencil and > paper. > > > > # The result is inside myfunc below > > > > > > > > myfunc<- function(x) {0.25*(9*x^4+6*x^2+1)} > > It is quite a long time I did school math but shouldn't be > > myfunc<- function(x) {0.25*(9*x^4-6*x^2+1)} > > > ^^^^^ > myfunc<- function(x) {0.25*(9*x^4-6*x^2+1)} > curve(myfunc,-1,1) > integrate(p2sq,-1,+1) > 0.4 with absolute error < 4.4e-15 > integrate(myfunc,-1,+1) > 0.4 with absolute error < 4.4e-15 > > Regards > Petr > > > > > > > > > > > # Below I made R to find the square of p2 > > > > p2sq<-function(x) {p2(x) * p2(x)} > > > > > > > > # Now I am trying to integrate both two function at > the same interval. > #Both > > functions should denote the square of p2 > > > > > > > > integrate(p2sq,-1,+1) > > > > # returns 0.4 with absolute error < 4.4e-15 > > > > > > > > integrate(myfunc,-1,+1) > > > > # returns 2.4 with absolute error < 2.7e-14 > > > > > > > > if there is no error in my calculations could you > please explain me why > > the two integrations return different results. Might > be that I am > > missing something from the theory. I would like to > thank you for your > > help > > > > > > > > Regards > > > > Alex > > > > ______________________________________________ > > [email protected] > mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, > reproducible code. > > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
