Odp: Integration in R
Hi r-help-bounces at r-project.org 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
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