Can a unnamed function be called in R?-CodePudding

Let's assume we have the following R code at the beginning of a R script named script.R:

function(input) { 
 output <- input*input
 return(output)
}

Is there a valid way to call this unnamed function in the reminder of script.R?

CodePudding user response：

This is possible, but it's not advisable. You would have to use eval and parse (or similar) to do it.

thisfile.R

function(input) {
 output <- input*input
 return(output)
}

# This can be many lines later:
fun <- eval(parse(text = paste(readLines("thisfile.R", 4), collapse = "\n")))

# Now you can use the function.
print(sapply(1:5, fun))

And sourcing it gives:

source("thisfile.R")
#> [1]  1  4  9 16 25

Not that although the function is stored as fun in the above example, you could use it directly, e.g.

print(sapply(1:5,
  eval(parse(text = paste(readLines("thisfile.R", 4), collapse = "\n")))))

And of course it would no longer work if you changed the filename or moved it to a different location.