[R] Integrate two function in R

[Ben Bolker]

Alaios <alaios <at> yahoo.com> writes:

> 
> Hello I have two function in R
> like 
> g(x)=2x-3
> and s(x)=5x^2+2
> 
> and I want to find the integrafl of the g(x)*s(x) inside the interval of [a,b]
> 

  Analytically or numerically?
  It sounds like you want the answer analytically, in which case R
can't do it, but it is an easy integral

  g(x)*s(x) = 10*x^3-15*x^2+4*x-6
  indefinite integral = 10/3*x^4 -15/3*x^3 + 4/2*x^2 - 6*x + C
  evaluate between a and b

  or if you can't do this (although this is a very basic integral)
you can try it on Wolfram alpha/the Mathematica integrator (google
for it)

  use ?integrate (surprisingly enough) for 1-D numerical integration