Interactive input

RStudio IDE
1

I have a program saved in a .R file. One of the challenges I have with it is that I have a statement that is supposed to read data from the keyboard which is not working. The statement is

num_itr <- scan(file = "", what = numeric(), n = 1, quiet = TRUE)

However, instead of the program stopping for input from the keyboard, it assigned an empty numeric value to num_itr.

What should I do to overcome this or is there an alternative code that I can use to read numeric data into a program running from a .R file?

2

Try changing file = "" to file = "stdin". According to the help documentation for scan, those should be equivalent, but on my system the latter works and former does not.

3

Thank you for your response. It actually work in that R stopped and was blinking for an input. However, the challenge is that after typing one numerical value to be read n = 1 being what was set, the program continued blinking in a manner that suggests it was waiting for more inputs. I tried stopping the operation by clicking the "interrupt" button. This equally failed to stop R and I had to choose the option of terminating R completely. This has happened twice.

I hope you may have other suggestion. Otherwise, your time is very much appreciated.

4

On my system (Linux Mint), ctrl-D will tell the script to stop waiting for input and move ahead (if possible).

I put the following code in a script (.R) file, ran it in a terminal with the Rscript command, and it behaved as expected. Does it work for you?

cat("Enter a number: ")
num_itr <- scan(file = "stdin", what = numeric(), n = 1, quiet = TRUE)
cat("The number entered is ", num_itr, "\n")

Created on 2025-12-29 with reprex v2.1.1