Introduction to formattable package
In formattable: Create 'Formattable' Data Structures

set.seed(123)

This package is designed for applying formatting on vectors and data frames to make data presentation easier, richer, more flexible and hopefully convey more information.

Atomic vectors are fundamental data structures in R. Some data can be read more easily with formatting. A numeric vector, for example, stores percentage numbers but is printed as typical floating numbers. This package provides functions to create data structures with predefined formatting rules so that these objects store the original data but are printed with formatting.

Several typical formattable numeric vectors are provided such as percent, comma, currency, accounting and scientific. These functions basically create numeric vectors with pre-defined formatting rules and parameters. For example,

library(formattable)
p <- percent(c(0.1, 0.02, 0.03, 0.12))
p

The percent vector is no different from a numeric vector but has a percentage representation when printed. It works with arithmetic operations and other common functions and preserves its formatting.

p + 0.05
p + percent(0.02)
p * 1.1

max(p)
mean(p)

It also works with subsetting and sub-assignment:

p[1:3]
p[[2]]

p[[3]] <- 0.05
p

balance <- accounting(c(1000, 500, 200, -150, 0, 1200))
balance
balance + 1000

These functions are specialized applications of what formattable() is designed to do. formattable() applies customizable formatting functions to objects of a wide range of classes like numeric, logical, factor, Date, data.frame, etc.

When applied to Date, formattable() uses format.Date() as the default formatter function. The following code creates a formattable Date vector that is printed in the format of %Y%m%d. However, it is not a plain integer or character vector but of Date class and still allows date calculations.

dates <- formattable(as.Date(c("2016-05-01", "2016-05-10")), format = "%Y%m%d")
dates
dates + 30

When applied to a logical vector, we can customize how TRUE and FALSE values are printed.

lv <- formattable(c(TRUE, FALSE, FALSE, TRUE), "yes", "no")
lv
!lv

Note that isTRUE() does not directly work with values of lv because isTRUE() uses identical(x, TRUE) and lv[[1]], as a formattable logical value is not identical to a plain TRUE.

lv[[1]]
isTRUE(lv[[1]])

If isTRUE() has to be applied, lv == TRUE returns a plain logical vector and works with isTRUE(). Other vectorized logical functions directly work with formattable logical vector with the formatting preserved.

all(lv)
any(lv)

All formattable functions work with matrices and arrays.

pm <- matrix(rnorm(6, 0.8, 0.1), 2, 3, 
  dimnames = list(c("a", "b"), c("X", "Y", "Z")))
pm

fpm <- percent(pm)
fpm

fpm["a", c("Y", "Z")]

pa <- array(rnorm(12, 0.8, 0.1), c(2, 3, 2))
pa

percent(pa)

When the formattable vectors are used as columns of a data frame, the formatting of each column is well preserved. A typical data frame may look more friendly with formattable column vectors. For example,

p <- data.frame(
  id = c(1, 2, 3, 4, 5), 
  name = c("A1", "A2", "B1", "B2", "C1"),
  balance = accounting(c(52500, 36150, 25000, 18300, 7600), format = "d"),
  growth = percent(c(0.3, 0.3, 0.1, 0.15, 0.15), format = "d"),
  ready = formattable(c(TRUE, TRUE, FALSE, FALSE, TRUE), "yes", "no"))
p