Formatting Decimal places in R

Question

I have a number, for example 1.128347132904321674821 that I would like to show as only two decimal places when output to screen (or written to a file). How does one do that?

x <- 1.128347132904321674821

EDIT:

The use of:

options(digits=2)

Has been suggested as a possible answer. Is there a way to specify this within a script for one-time use? When I add it to my script it doesn't seem to do anything different and I'm not interested in a lot of re-typing to format each number (I'm automating a very large report).

--

Answer: round(x, digits=2)

Answer 1

Looks to me like to would be something like

library(tutoR)
format(1.128347132904321674821, 2)

Per a little online help.

Answer 2

Background: Some answers suggested on this page (e.g., signif, options(digits=...)) do not guarantee that a certain number of decimals are displayed for an arbitrary number. I presume this is a design feature in R whereby good scientific practice involves showing a certain number of digits based on principles of "significant figures". However, in many domains (e.g., APA style, business reports) formatting requirements dictate that a certain number of decimal places are displayed. This is often done for consistency and standardisation purposes rather than being concerned with significant figures.

Solution:

The following code shows exactly two decimal places for the number x.

format(round(x, 2), nsmall = 2)

For example:

format(round(1.20, 2), nsmall = 2)
# [1] "1.20"
format(round(1, 2), nsmall = 2)
# [1] "1.00"
format(round(1.1234, 2), nsmall = 2)
# [1] "1.12"

A more general function is as follows where x is the number and k is the number of decimals to show. trimws removes any leading white space which can be useful if you have a vector of numbers.

specify_decimal <- function(x, k) trimws(format(round(x, k), nsmall=k))

E.g.,

specify_decimal(1234, 5)
# [1] "1234.00000"
specify_decimal(0.1234, 5)
# [1] "0.12340"

Answer 3

for 2 decimal places assuming that you want to keep trailing zeros

sprintf(5.5, fmt = '%#.2f')

which gives

[1] "5.50"

As @mpag mentions below, it seems R can sometimes give unexpected values with this and the round method e.g. sprintf(5.5550, fmt='%#.2f') gives 5.55, not 5.56

Answer 4

Something like that :

options(digits=2)

Definition of digits option :

digits: controls the number of digits to print when printing numeric values.

Answer 5

Well, the two that come to mind are

fixed(1.128347132904321674821, digits=2)

or if you prefer siginificant digits to fixed digits then;

signif(1.128347132904321674821,digits=3)

Answer 6

Check functions prettyNum, format

to have trialling zeros (123.1240 for example) use sprintf(x, fmt='%#.4g')