CODEWITHSUNDEEP
r
Smirk
Smirk

Reputation: 59

compute an integration

Here is my integrand()

 integrand<-function(x,vecC)
  {
   as.numeric((2/(b-a))*vecC%*%as.matrix(cos((x-hat.a)
 *(seq(0,N-1,length=N)*pi/(b-a)))))
  }

it can produce the value. For example, for 

 a<-1
 b<-10
 vecC<-t(as.matrix(rnorm(80)))
 hat.a<--1.2
 N<-80

I get

 > integrand(1.4,vecC)
 [1] -0.3635195

but I met problem when I run the following code for integration

 > integrate(function(x){integrand(x,vecC)},upper = 3.4,lower = 1)$value

and the error message is

Error in integrate(function(x) { : evaluation of function gave a result of wrong length In addition: Warning message: In (x - hat.a) * (seq(0, N - 1, length = N) * pi/(b - a)) : longer object length is not a multiple of shorter object length

Upvotes: 1

Views: 65

Answers (1)

Bhas
Bhas

Reputation: 1834

If you read the help page for integrate you will see that the function passed to integrate should return a vector.

So the solution to your error is to use Vectorize like this Define your function separately as

 f <- function(x){integrand(x,vecC)}

Now define a vectorized version of this function like so

 fv <- Vectorize(f,"x")

and then 

integrate(fv,upper = 3.4,lower = 1)$value

will give you a result.

Upvotes: 2

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