What tilde command do

Question

I saw in a tutorial about regression modeling the following command :

myFormula <- Species ~ Sepal.Length + Sepal.Width + Petal.Length + Petal.Width

What exactly does this command do, and what is the role of ~ (tilde) in the command?

Answer 1

Something that characterizes formulas in R is the tilde operator ~. With this operator, you can actually say: "capture the meaning of this code, without evaluating it right away”. That also explains why you can think of a formula in R as a "quoting" operator.

But what does a formula exactly look like? Take a closer look at the following line of code:

# A formula
c <- y ~ x
d <- y ~ x + b
# Double check the class of `c`
class(c)

'formula'

The variable on the left-hand side of a tilde (~) is called the "dependent variable", while the variables on the right-hand side are called the "independent variables" and are joined by plus signs +.