Print Out Variables Passed Into Functions

Question

I come from a python background but I'm new to R (need to learn it in a hurry), stuck at an issue:

I am developing a function to print out the variables passed into my function, kinda simple.

hello_world <- function(fn, num) {
    print("The stuff you sent in were "$fn" and "$num")
}

so if I call hello world as such:

hello_world("foo", 3:5)

I should see

The stuff you sent in were "foo" and "3:5"

I tried print("$foo", "$num")...still having issues. How can I do this without using sprint?

Remove the $, from fn and num and use paste i.e. paste("The stuff you sent in were", fn, ' and ', num) — akrun
– akrun, Commented Jun 3, 2022 at 18:57

akrun · Accepted Answer · 2022-06-03 19:05:45Z

1

We could use deparse/substitute to get the input as it is from 'num', and then create a single string with paste

hello_world <- function(fn, num) {
      num <- deparse(substitute(num))
      cat(paste0("The stuff you sent in were ", '"', fn, '"',
              " and ", '"', num, '"'), "\n")
                    }

-testing

> hello_world("foo", 3:5)
The stuff you sent in were "foo" and "3:5"

answered Jun 3, 2022 at 19:05

akrun

891k38 gold badges590 silver badges700 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Rui Barradas · Accepted Answer · 2022-06-03 19:03:32Z

Use paste to assemble the string to be printed. And note that since 3:5 is a vector, the first paste uses argument collapse.
I have also included 3 different ways of printing.

hello_world <- function(fn, num) {
  num_string <- paste(num, collapse = ",")
  msg <- paste("The stuff you sent in were", dQuote(fn), "and", dQuote(num_string))
  # 3 ways of printing
  print(msg)
  cat(msg, "\n")    # needs the newline character
  message(msg)      # this will default to printing in red
} 
hello_world("foo", 3:5)
#> [1] "The stuff you sent in were “foo” and “3,4,5”"
#> The stuff you sent in were “foo” and “3,4,5”
#> The stuff you sent in were “foo” and “3,4,5”

^{Created on 2022-06-03 by the reprex package (v2.0.1)}

Mohamed Desouky · Accepted Answer · 2022-06-03 19:08:57Z

1

Just use cat instead of print ,

hello_world <- function(fn, num) {
  cat("The stuff you sent in were \"" , fn , "\" and \"" , num , "\"" , sep = "")
} 

hello_world("foo", 3:5)
#> The stuff you sent in were "foo" and "345"

hello_world("foo", "3:5")
#> The stuff you sent in were "foo" and "3:5"

^{Created on 2022-06-03 by the reprex package (v2.0.1)}

answered Jun 3, 2022 at 19:08

Mohamed Desouky

4,4552 gold badges6 silver badges21 bronze badges

Comments

Matt · Accepted Answer · 2022-06-03 19:33:03Z

Here's an option where you don't have to specify your parameters:

library(purrr)

hello_world <- function(fn, num) {
  params <- as.character(match.call()[-1])
  out <- sub(paste(map_chr(params, ~paste("`", ., "`",  " and")), collapse = ' '), pattern = " [[:alpha:]]*$", replacement = "")
  paste0('The stuff you sent in were ', out)
} 

hello_world('foo', 3:5)
#> [1] "The stuff you sent in were ` foo `  and ` 3:5 ` "

So you could extend this to something like:

library(purrr)

hello_world <- function(fn, num, apple, banana, cheeseburger) {
  params <- as.character(match.call()[-1])
  out <- sub(paste(map_chr(params, ~paste("`", ., "`",  " and")), collapse = ' '), pattern = " [[:alpha:]]*$", replacement = "")
  paste0('The stuff you sent in were ', out)
} 

hello_world('foo', 3:5, 'yes', 'no', 'definitely')
#> [1] "The stuff you sent in were ` foo `  and ` 3:5 `  and ` yes `  and ` no `  and ` definitely ` "

Collectives™ on Stack Overflow

Print Out Variables Passed Into Functions

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related