String interpolation (f-strings for R)

Interpolate R expressions into a string, like 'Python' f-strings. Anything inside curly braces is evaluated in the calling environment and inserted into the string. Doubled braces are treated as a single literal brace.

Usage

f(..., .envir = parent.frame())

Arguments

...

one or more strings containing {expr} placeholders

.envir

the environment in which to evaluate the placeholders (defaults to the calling environment)

Value

A character vector the same length as the input, with every {expr} replaced by its evaluated, comma-collapsed value.

Note

f is also a popular name for throwaway functions, so be aware it may mask (or be masked by) a local f of your own.

Author

Ben Wiseman, benjamin.h.wiseman@gmail.com

Examples

name <- "Ben"
n    <- 2
f("Hi {name}, you have {n} new messages")
#> [1] "Hi Ben, you have 2 new messages"
f("{n} + {n} = {n + n}")
#> [1] "2 + 2 = 4"

# vectors are collapsed with ", "
f("today's letters: {head(LETTERS, n)}")
#> [1] "today's letters: A, B"