Page 55 - Applied Statistics with R

3.3. PROGRAMMING BASICS 55

1
2
̂ = ∑( − ̄ ) 2

=1
get_var = function(x, biased = FALSE) {
n = length(x) - 1 * !biased
(1 / n) * sum((x - mean(x)) ^ 2)
}

get_var(test_sample)

## [1] 14.56753

get_var(test_sample, biased = FALSE)

## [1] 14.56753

var(test_sample)

## [1] 14.56753

We see the function is working as expected, and when returning the unbiased
estimate it matches R’s built in function var(). Finally, let’s examine the biased
2
estimate of .
get_var(test_sample, biased = TRUE)

## [1] 13.11077