You are missing basic algebra skills!

You had:

myfunc<- function(x) {0.25*(9*x^4 + 6*x^2 + 1)}

This should be:

myfunc<- function(x) {0.25*(9*x^4 - 6*x^2 + 1)}

Ravi.

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

Ravi Varadhan, Ph.D.

Assistant Professor,

Division of Geriatric Medicine and Gerontology School of Medicine Johns

Hopkins University

Ph. (410) 502-2619

email:

[hidden email]
-----Original Message-----

From:

[hidden email] [mailto:

[hidden email]] On

Behalf Of Alaios

Sent: Monday, January 10, 2011 9:13 AM

To:

[hidden email]
Subject: [R] Integration in R

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)}

# 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

______________________________________________

[hidden email] mailing list

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.

______________________________________________

[hidden email] mailing list

https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.