Programatically Create Formulas in R

I’m working on a prototype of a tool using R to create some regressions. I’d like to take in independent and dependent variables as character vectors and use those to create a formula. It took me a minute to figure out how to programatically create a formula. It’s a bit tricky because formula require unquoted objects (symbols).

The trick is to use the function reformulate() (thanks StackOverflow).

The syntax is reformulate(x_vars, y_var)

form <- reformulate(c("x1", "x2"), "y")
form

y ~ x1 + x2

Nice. Throw it into a function.

make_lm <- function(.data, y, x) {
  form <- reformulate(x, y)
  lm(form, .data)
}

Now try it out :)

make_lm(
  iris, 
  y = "Petal.Width",
  x = c("Sepal.Length", "Petal.Length")
)

Call:
lm(formula = form, data = .data)

Coefficients:
 (Intercept)  Sepal.Length  Petal.Length  
   -0.008996     -0.082218      0.449376  

This can be a pretty hand pattern in package development. I hope it helps you.