# [R] Integrate two function in R

Kjetil Halvorsen kjetilbrinchmannhalvorsen at gmail.com
Thu Dec 16 15:11:33 CET 2010

```see inline.

On Thu, Dec 16, 2010 at 10:11 AM, Ben Bolker <bbolker at gmail.com> wrote:
> 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)

Or a free software alternative: sage
http://www.sagemath.org/

kjetil

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