Question

I am getting an error in R and am unsure how to correct it. I am getting an error from the r2 line, "Error in xc[1:(n - 2)] : only 0's may be mixed with negative subscripts."

tmpFn <- function(xVec)
{
xc <- xVec - mean(xVec)
denom <- sum(xc^2)
n <- length(x)
r1 <- sum( xc[2:n] * xc[1:(n-1)] )/denom
r2 <- sum( xc[3:n] * xc[1:(n-2)] )/denom
list(r1 = r1, r2 = r2)
}

tmpFn(seq(2, 56, 3))

10. (a) Given a vector (x1, ..., xn), the sample autocorrelation of lag k is defined to be Tk = i=k+1(Xi - &)(x;_k- Thus SL(Xi - #)(x-1 - 3) (^2 — 2) (х| — х) +:.. + (хр — х) (хn-1 — г) Write a function tmpFn(xVec) which takes a single argument xVec which is a vector and returns a Exercises 3 Page 7 Jun 7, 2013(21:45) list of two values: rj and r2. In particular, find r1 and r2 for the vector (2, 5, 8,..., 53,56)

Answer 1

I ran your code and it is running perfectly fine. Just changed the 3rd line of the function as shown.

tmpFn <- function(xVec)
{
xc <- xVec - mean(xVec)
denom <- sum(xc^2)
n <- length(xVec)
r1 <- sum( xc[2:n] * xc[1:(n-1)] )/denom
r2 <- sum( xc[3:n] * xc[1:(n-2)] )/denom
list(r1 = r1, r2 = r2)
}
tmpFn(seq(2, 56, 3))

I got the output as

$r1
[1] 0.8421053

$r2
[1] 0.6859649