In R, formatting numbers is an essential task, especially when working with numerical data. This tutorial will cover how to format decimal places in R, including rounding and displaying trailing zeros.
Introduction to Formatting Numbers
R provides several ways to format numbers, including the use of functions such as format(), round(), formatC(), and sprintf(). Each function has its own strengths and weaknesses, and choosing the right one depends on your specific needs.
Using round() and format()
One common approach is to combine round() with format() to display a specified number of decimal places. The round() function rounds a number to the nearest integer or to a given number of decimals, while format() converts the result to a character string.
Here’s an example:
x <- 1.128347132904321674821
y <- format(round(x, 2), nsmall = 2)
print(y) # Output: "1.13"
In this example, round(x, 2) rounds the number to two decimal places, and format() converts the result to a character string with two decimal places.
Using formatC()
Another approach is to use formatC(), which provides more control over the formatting process.
x <- 1111111234.6547389758965789345
y <- formatC(x, digits = 8, format = "f")
print(y) # Output: "1111111234.65473890"
In this example, formatC() formats the number as a floating-point number with eight decimal places.
Using sprintf()
sprintf() is another function that can be used to format numbers in R.
x <- 5.5
y <- sprintf("%.2f", x)
print(y) # Output: "5.50"
In this example, sprintf() formats the number as a floating-point number with two decimal places.
Preserving Trailing Zeros
When formatting numbers, it’s often important to preserve trailing zeros. The format() function can be used with the nsmall argument to achieve this.
x <- 1.2
y <- format(round(x, 2), nsmall = 2)
print(y) # Output: "1.20"
In this example, format() preserves the trailing zero.
Creating a Custom Function
If you need to format numbers frequently, you can create a custom function that combines the round() and format() functions.
specify_decimal <- function(x, k) {
trimws(format(round(x, k), nsmall = k))
}
This function takes two arguments: x, the number to be formatted, and k, the number of decimal places. You can use this function like this:
x <- 1234
y <- specify_decimal(x, 5)
print(y) # Output: "1234.00000"
Conclusion
Formatting numbers in R is a straightforward process that requires choosing the right function for your specific needs. By using round(), format(), formatC(), or sprintf(), you can display numbers with the desired number of decimal places and preserve trailing zeros when necessary.