Printing an Output of a Program in R

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Printing output in R

When working with R in an interactive mode, you don’t need to use any functions or methods to print the result of your expressions; it will print them automatically.

Simply typing a variable or expression will print its value.

data <- 42

data

# [1]  42

However, you need functions to see the output if you are working in a script where you have written a program.

Here are six ways you can use to print the output of a program:

  1. Using print()
  2. Using cat()
  3. Using message(), warning(), and stop()
  4. Using sprintf()
  5. Using paste() / paste0()
  6. Writing to a file

Method 1: Using print()

The print() function is explicitly used to display the value of an object. It is a standard method for printing output to the console.

Visual Representation of print() Function in R

Basic print() usage

data <- 1:5

print(data)

# [1] 1 2 3 4 5

Passing “digits” argument

Passing digits argument to the print() function

data <- 1 / 5
data2 <- 111 / 23
data3 <- 10900 / 2966

print(data, digits = 2)
print(data2, digits = 3)
print(data3, digits = 4)

# [1] 0.2
# [1] 4.83
# [1] 3.675

Handling NA values

If you pass the na.print argument to empty, it will replace NA values with nothing in the output.

Visualization of Passing na.print argument to print() function

mat <- matrix(c(1, NA, 3, 4, NA, 6, 7, 8, NA),
   nrow = 3, byrow = TRUE
)

print(mat)
cat("After passing na.print argument to empty", "\n")

print(mat, na.print = "")

Figure of Passing na.print argument to print() function

Method 2: Using cat()

The cat() function concatenates and prints its arguments. It helps print custom messages or formatting output. It does not add quotes. For a cleaner console output, you can use this approach.

x <- 21

cat("The value of x is:", x, "\n")

# The value of x is: 21

The cat() method does not automatically add a new line, as you can see from the above code. We added a newline character “\n” manually. 

It cannot handle complex objects like a matrix.

mat <- matrix(1:4, nrow = 2)

cat(mat)

# 1 2 3 4%

You can see that the console output is wrong, and it does not look like a matrix.

Method 3: Using message(), warning(), and stop()

The message() prints a message but does not stop the execution of a function.

The warning() issues a warning message but, like message(), allows the execution to continue.

The stop() prints an error message and stops the execution.

message("This is a message.")

warning("This is a warning.")

Output

This is a message.

Warning message:
This is a warning.

Method 4: Using sprintf() for Formatted Strings

The sprintf() function formats strings (similar to printf() in C/C++). It’s helpful when you need to format numbers or strings before printing.

x <- 19

sprintf("The value of x is: %f", x)

Output

[1] "The value of x is: 19.000000"

Method 5: Using paste() / paste0()

The paste() function inserts spaces by default. The paste0() function concatenates without spaces.

paste("AI", "Learning")
# "AI Learning"

paste0("Hello", "world")
# "AILearning"

Method 6: Writing to a file

To print output to a file, you can use cat(), write.table(), or similar functions with a file connection.

x <- 1921

cat("The value of x is:", x, file = "output.txt", append = TRUE)

Output

Output of printing a variable in file in R

That’s it!

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