How to format a number as percentage in R?

Even later:

As pointed out by @DzimitryM, percent() has been "retired" in favor of label_percent(), which is a synonym for the old percent_format() function.

label_percent() returns a function, so to use it, you need an extra pair of parentheses.

library(scales)x <- c(-1, 0, 0.1, 0.555555, 1, 100)label_percent()(x)## [1] "-100%"   "0%"      "10%"     "56%"     "100%"    "10 000%"

Customize this by adding arguments inside the first set of parentheses.

label_percent(big.mark = ",", suffix = " percent")(x)## [1] "-100 percent"   "0 percent"      "10 percent"    ## [4] "56 percent"     "100 percent"    "10,000 percent"

An update, several years later:

These days there is a percent function in the scales package, as documented in krlmlr's answer. Use that instead of my hand-rolled solution.

Try something like

percent <- function(x, digits = 2, format = "f", ...) {  paste0(formatC(100 * x, format = format, digits = digits, ...), "%")}

With usage, e.g.,

x <- c(-1, 0, 0.1, 0.555555, 1, 100)percent(x)

(If you prefer, change the format from "f" to "g".)

Check out the scales package. It used to be a part of ggplot2, I think.

library('scales')percent((1:10) / 100)#  [1] "1%"  "2%"  "3%"  "4%"  "5%"  "6%"  "7%"  "8%"  "9%"  "10%"

The built-in logic for detecting the precision should work well enough for most cases.

percent((1:10) / 1000)#  [1] "0.1%" "0.2%" "0.3%" "0.4%" "0.5%" "0.6%" "0.7%" "0.8%" "0.9%" "1.0%"percent((1:10) / 100000)#  [1] "0.001%" "0.002%" "0.003%" "0.004%" "0.005%" "0.006%" "0.007%" "0.008%"#  [9] "0.009%" "0.010%"percent(sqrt(seq(0, 1, by=0.1)))#  [1] "0%"   "32%"  "45%"  "55%"  "63%"  "71%"  "77%"  "84%"  "89%"  "95%" # [11] "100%"percent(seq(0, 0.1, by=0.01) ** 2)#  [1] "0.00%" "0.01%" "0.04%" "0.09%" "0.16%" "0.25%" "0.36%" "0.49%" "0.64%"# [10] "0.81%" "1.00%"

Check out the percent function from the formattable package:

library(formattable)x <- c(0.23, 0.95, 0.3)percent(x)[1] 23.00% 95.00% 30.00%