What does the tilde mean in this context of R code

Question

Fx=purrr::map(CDF, ~ tibble(
                    severity=severities$severity,
                    inclusive=severities$inclusive,
                    Fx=.x(severities$severity, severities$inclusive))))

raw_df <- tibble::tribble(
    ~"segment", ~"limit", ~"attach", ~"pct_written", ~"premium", ~"product", ~"lalae_ratio",
    "",    50000,      1000,            0.5,     273456,    "prod1",           0.65,
    "",    20000,      2000,            0.5,     285760,    "prod2",           0.65,
    "",    2e+05,      3000,            0.5,     956456,    "prod3",           0.65,
    "",    10000,       300,            0.5,      90890,    "prod4",           0.65)

I can sort of guess it, but I do not have a precise definition of what it does.

This is different from:

dependent_variable ~ independent_variables

@Sotos Your duplicate is fairly uninformative since the question is about a specific use of `~` which isn’t covered in the other question. — Konrad Rudolph, Jun 18 '19 at 14:15

score 5 · Answer 1 · answered Jun 18 '19 at 14:17

The tilde operator in R is a general operator that creates a formula object.

However, the usage in your specific pieces of code is a special case of that: purrr co-opts formulas to implement an anonymous function notation. You can read more in the purrr introduction. But briefly, the usage

purrr::map(data, ~ expression_with(.x))

Is equivalent to

purrr::map(data, function (.x) expression_with(.x))

The second piece of code does something different still, and that usage is described in the documentation of the tribble function.

What does the tilde mean in this context of R code

1 Answers1