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Require c() to be applied before relatively expensive vectorized functions

Source: R/inner_combine_linter.R
inner_combine_linter.Rd

as.Date(c(a, b)) is logically equivalent to c(as.Date(a), as.Date(b)). The same equivalence holds for several other vectorized functions like as.POSIXct() and math functions like sin(). The former is to be preferred so that the most expensive part of the operation (as.Date()) is applied only once.

Usage

inner_combine_linter()

Details

Note that strptime() has one idiosyncrasy to be aware of, namely that auto-detected format= is set by the first matching input, which means that a case like c(as.POSIXct("2024-01-01"), as.POSIXct("2024-01-01 01:02:03")) gives different results to as.POSIXct(c("2024-01-01", "2024-01-01 01:02:03")). This false positive is rare; a workaround where possible is to use consistent formatting, i.e., "2024-01-01 00:00:00" in the example.

See also

linters for a complete list of linters available in lintr.

Tags

consistency, efficiency, readability

Examples

# will produce lints
lint(
  text = "c(log10(x), log10(y), log10(z))",
  linters = inner_combine_linter()
)
#> <text>:1:1: warning: [inner_combine_linter] Combine inputs to vectorized functions first to take full advantage of vectorization, e.g., log10(c(x, y)) only runs the more expensive log10() once as compared to c(log10(x), log10(y)).
#> c(log10(x), log10(y), log10(z))
#> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# okay
lint(
  text = "log10(c(x, y, z))",
  linters = inner_combine_linter()
)
#> ℹ No lints found.

lint(
  text = "c(log(x, base = 10), log10(x, base = 2))",
  linters = inner_combine_linter()
)
#> ℹ No lints found.