Package {deduped}

Deduplicate a vectorized function to act on unique elements

Description

Converts a vectorized function into one that only performs the computations on unique values in the first argument. The result is then expanded so that it is the same as if the computation was performed on all elements.

Note: This only works with functions that preserve length and order.

Usage

deduped(f, verbose = NULL)

Arguments

Details

We make a best effort to preserve the two main cases for named inputs:

1. If f() drops names, names are dropped in the output.

2. Otherwise, we preserve the names from the input x. We cannot reliably re-expand the names from the deduped output, since duplicate values would always map back to their first occurrence's name.

Value

Deduplicated version of f.

Examples

x <- sample(LETTERS, 10)
x

large_x <- sample(rep(x, 10))
length(large_x)

slow_func <- function(x) {
  for (i in x) {
    Sys.sleep(0.001)
  }
  tolower(x)
}

system.time({
  y1 <- slow_func(large_x)
})

system.time({
  y2 <- deduped(slow_func)(large_x)
})

all(y1 == y2)

Deduplicate the first argument in an expression

Description

This is a convenience wrapper for deduped() to allow it to be piped into an expression. It will recursively parse the first arguments of the expression call tree to find the bottom – when the first argument is not itself a function call.

• Without nesting: f(x, ...) |> with_deduped() is equivalent to ⁠deduped(\(.z) f(.z, ...))(x)⁠.

• With nesting: f(g(x, g2), f2) |> with_deduped() is equivalent to ⁠deduped(\(.z) f(g(.z, g2), f2))(x)⁠.

Usage

with_deduped(expr, env = parent.frame(), verbose = NULL)

Arguments

Details

with_deduped() reconstructs the wrapper function on every call, so it is best suited for one-off or interactive use. For repeated calls such as inside a loop, build the wrapper once with deduped() instead:

# Preferred for loops:
deduped_f <- deduped(slow_func)
for (...) deduped_f(x)

# Rather than:
for (...) slow_func(x) |> with_deduped()

Value

The result of evaluating the expression.

Examples

x <- sample(LETTERS, 10)
x

large_x <- sample(rep(x, 10))
length(large_x)

slow_func <- function(x) {
  for (i in x) {
    Sys.sleep(0.001)
  }
  tolower(x)
}

system.time({
  y1 <- slow_func(large_x)
})


system.time({
  y2 <- with_deduped(slow_func(large_x))

  # Can also use the R pipe (R >= 4.1.0) or magrittr pipe, for convenience.
  # slow_func(large_x) |> with_deduped()
})

all(y1 == y2)