lintr (version 3.2.0)

nrow_subset_linter: Block usage of nrow(subset(x, .))

Description

Using nrow(subset(x, condition)) to count the instances where condition applies inefficiently requires doing a full subset of x just to count the number of rows in the resulting subset. There are a number of equivalent expressions that don't require the full subset, e.g. with(x, sum(condition)) (or, more generically, with(x, sum(condition, na.rm = TRUE))).

Usage

nrow_subset_linter()

Tags

best_practices, consistency, efficiency

See Also

linters for a complete list of linters available in lintr.

Examples

# will produce lints
lint(
  text = "nrow(subset(x, is_treatment))",
  linters = nrow_subset_linter()
)

lint(
  text = "nrow(filter(x, is_treatment))",
  linters = nrow_subset_linter()
)

lint(
  text = "x %>% filter(x, is_treatment) %>% nrow()",
  linters = nrow_subset_linter()
)

# okay
lint(
  text = "with(x, sum(is_treatment, na.rm = TRUE))",
  linters = nrow_subset_linter()
)