Getting User Input

In the previous lesson, you created a welcome message for the Bill Split Calculator. Now, add the functionality to collect user input for the bill calculation.

After your existing welcome message, read three inputs from the user:

1. The total bill amount
2. The tip percentage (as a whole number, e.g., 15 for 15%)
3. The number of people splitting the bill

In R scripts that run non-interactively (like on this platform), input is read from the standard input stream. To do this, first open a connection to stdin using file(), then read each line with readLines(), and close the connection when done:

con <- file("stdin", "r")
bill <- as.numeric(suppressWarnings(readLines(con, n = 1)))
tip_percent <- as.numeric(suppressWarnings(readLines(con, n = 1)))
people <- as.numeric(suppressWarnings(readLines(con, n = 1)))
close(con)

Here is what each part does:

• file("stdin", "r"): opens the standard input stream for reading and stores it in con
• readLines(con, n = 1): reads exactly one line from that connection. Note: readLines() is different from readline(): readLines() works with file connections (including stdin) and can read multiple lines at once using n =, while readline() only works interactively in the R console
• suppressWarnings(...): silences harmless warnings that appear when reading from stdin this way. When R reads from stdin in a script, it sometimes produces a warning like "incomplete final line" even when everything works correctly. Wrapping the call in suppressWarnings() hides these messages so they don't clutter your output. It does not affect the values being read
• as.numeric(...): converts the text input to a number
• close(con): closes the connection after all inputs are read

Store the three values in variables named bill, tip_percent, and people.

After reading the inputs, display a confirmation message showing what was entered in the following format:

Bill: $[bill]
Tip: [tip_percent]%
People: [people]

Use cat() for all output and include newline characters \n where needed. Use sep = "" in each cat() call to avoid unwanted spaces.

By default, cat() inserts a space between each item it prints. For example:

cat("Bill: $", 120, "\n")   # prints: Bill: $ 120 

Notice the unwanted spaces between $ and 120, and before the newline. Adding sep = "" tells cat() to use an empty string as the separator instead, so nothing is inserted between items:

cat("Bill: $", 120, "\n", sep = "")   # prints: Bill: $120

Apply this pattern to all three confirmation lines:

cat("Bill: $", bill, "\n", sep = "")
cat("Tip: ", tip_percent, "%\n", sep = "")
cat("People: ", people, "\n", sep = "")

For example, if the inputs are 120, 18, and 4, the complete output should be:

Welcome to the Bill Split Calculator!
Let's split your bill fairly.
Bill: $120
Tip: 18%
People: 4