
Problem –
You want to print the value of a variable or expression.
Solution –
It is very easy to print something to the screen just type the variable name or expression at the command prompt and R will print it for you.
> pi
[1] 3.141593
> sqrt(4)
[1] 2
When you enter expression like these, R evaluates the expression and then implicitly calls the print function. The following expression is same as the above one.
> print(pi)
[1] 3.141593
> print(sqrt(4))
[1] 2
You can also use print to show matrices and list. print function knows how to display them to the user.
> print(matrix(c(1, 2, 3, 4), 2, 2))
[,1] [,2]
[1,] 1 3
[2,] 2 4
> print(list("a","b","c"))
[[1]]
[1] "a"
[[2]]
[1] "b"
[[3]]
[1] "c"
But there is one limitation to print function. It only prints one item at a time. If you try to print multiple items together, it won’t work.
> print("Hello world", 2*pi)
[1] "Hello world"
The cat function is an alternative to print function that let’s you concatenate multiple items into a continuous output.
> cat("Hello world", 2*pi)
Hello world 6.283185