Sum of Squared Error

sum_squares(x, y = x)

Arguments

x	numeric vector
y	optional, numeric vector, same length as `x`

either the sum of squared errors for x (if y is left out), or the cross-product of two vectors x with y

The sum of squared errors for a length $n$ vector $x$ will equal

$$S_{xx} = \sum_i^n(x - \overline{x})^2,$$

where $\overline{x}$ is the mean of $x$.

The cross-product is

$$S_{xy} = \sum_i^n (x - \overline{x})(y - \overline{y})$$

# the sum of squared errors for x
x <- rnorm(10)
sum_squares(x)
#> [1] 6.209723

# a cross-product
y <- rnorm(10)
sum_squares(x, y)
#> [1] 3.532127