An alternative to the internal do.call

Description

The do.call can be somewhat slow, especially when working with large objects. This function is based upon the suggestions from Hadley Wickham on the R mailing list, see here. Also thanks to Tommy at StackOverflow for suggesting how to handle double and triple colon operators, ::, further enhancing the function.

Usage

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fastDoCall(what, args, quote = FALSE, envir = parent.frame())

Arguments

what

either a function or a non-empty character string naming the function to be called.

args

a list of arguments to the function call. The names attribute of args gives the argument names.

quote

a logical value indicating whether to quote the arguments.

envir

an environment within which to evaluate the call. This will be most useful if what is a character string and the arguments are symbols or quoted expressions.

Note

While the function attempts to do most of what do.call can it has limitations. It can currently not parse the example code from the original function: do.call(paste, list(as.name("A"), as.name("B")), quote = TRUE) and the functionality of quote has not been thoroughly tested.

Examples

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fastDoCall("complex", list(imaginary = 1:3))

## if we already have a list (e.g. a data frame)
## we need c() to add further arguments
tmp <- expand.grid(letters[1:2], 1:3, c("+", "-"))
fastDoCall("paste", c(tmp, sep = ""))

## examples of where objects will be found.
A <- 2
f <- function(x) print(x^2)
env <- new.env()
assign("A", 10, envir = env)
assign("f", f, envir = env)
f <- function(x) print(x)
f(A)                                      # 2
fastDoCall("f", list(A))                     # 2
fastDoCall("f", list(A), envir = env)        # 4
fastDoCall(f, list(A), envir = env)          # 2
fastDoCall("f", list(quote(A)), envir = env) # 100
fastDoCall(f, list(quote(A)), envir = env)   # 10
fastDoCall("f", list(as.name("A")), envir = env) # 100

eval(call("f", A))                      # 2
eval(call("f", quote(A)))               # 2
eval(call("f", A), envir = env)         # 4
eval(call("f", quote(A)), envir = env)  # 100

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