formatdown

Formatting Numbers in R Markdown Documents

Provides a small set of tools for formatting numbers in R markdown documents (file type .Rmd or .qmd). Converts a numerical vector to character strings in power-of-ten form, decimal form, or measurement-units form; all are math-delimited within quotation marks for rendering as inline equations. Useful for rendering numerical scalars using inline R code chunks or for rendering numerical columns in tables.

Introduction

In professional technical prose, large and small numbers are generally typeset using powers of ten notation. For example, Planck’s constant would be typeset as $6.63 \times 10^{-34}>\mathrm{J,Hz^{-1}}$ rather than the familiar forms we use in communicating with computers, such as 6.63*10^-34 or 6.63E-34.

The functions in this package help an author of an R markdown document convert large and small numbers to character strings, formatted using powers-of-ten notation. In addition, decimal numbers and text can be formatted with the same font face and size as the power-of-ten numbers for a consistent typeface across all columns of a data table.

Formatting tools include:

format_numbers()
Convert a numeric vector to a math-delimited character vector in which the numbers can be formatted in scientific or engineering power-of-ten notation or in decimal form.

format_sci()
Convenience function. A wrapper around format_numbers() for scientific notation.

format_engr()
Convenience function. A wrapper around format_numbers() for engineering notation.

format_dcml()
Convenience function. A wrapper around format_numbers() for decimal notation.

format_text()
Convert a character vector to math-delimited character vector. Useful for creating a consistent typeface across all columns of a table.

formatdown_options()
Global options are provided for arguments that users would likely prefer to set once in a document instead of repeating in every function call. For example, some users prefer a comma decimal marker (“,”) throughout a document.

Usage

# Packages
library("formatdown")
library("data.table")
library("knitr")

Scalar values.   Typically rendered inline:

x <- 101300

# Scientific notation
format_numbers(x, digits = 4, format = "sci")
#> [1] "$1.013 \\times 10^{5}$"

# Engineering notation
format_numbers(x, digits = 4, format = "engr")
#> [1] "$101.3 \\times 10^{3}$"

# Decimal notation
format_numbers(x, digits = 4, format = "dcml")
#> [1] "$101300$"

# With measurement units
units(x) <- "Pa"
units(x) <- "hPa"
format_dcml(x)
#> [1] "$1013\\>\\mathrm{hPa}$"

which, in an .Rmd or .qmd output document, are rendered using inline R code as

Data frame.   Typically rendered in a table. We independently format columns from the metals data frame included with formatdown.

# View the data set
metals
#>            metal  dens  thrm_exp thrm_cond  elast_mod
#>           <char> <num>     <num>     <num>      <num>
#> 1: aluminum 6061  2700 2.430e-05    155.77 7.3084e+10
#> 2:        copper  8900 1.656e-05    392.88 1.1721e+11
#> 3:          lead 11340 5.274e-05     37.04 1.3790e+10
#> 4:      platinum 21450 9.000e-06     69.23 1.4686e+11
#> 5:    steel 1020  7850 1.134e-05     46.73 2.0684e+11
#> 6:      titanium  4850 9.360e-06      7.44 1.0204e+11

# First column in text format
DT <- copy(metals)
DT$metal <- format_text(DT$metal)

# Density and thermal conductivity in decimal form
cols_we_want <- c("dens", "thrm_cond")
DT[, cols_we_want] <- lapply(DT[, ..cols_we_want], function(x) format_dcml(x, 3))

# Thermal expansion in engineering format
DT$thrm_exp <- format_engr(DT$thrm_exp, 3)

# Elastic modulus in units form
units(DT$elast_mod) <- "Pa"
units(DT$elast_mod) <- "GPa"
DT$elast_mod <- format_dcml(DT$elast_mod, 3)

# Render in document
knitr::kable(DT, align = "r", caption = "Table 1: Properties of metals.", col.names = c("Metal",
    "Density [kg/m$^3$]", "Therm. expan. [m/m K$^{-1}$]", "Therm. cond. [W/m K$^{-1}$]",
    "Elastic modulus"))

Table 1: Properties of metals.

Options.   For users who prefer a comma as the decimal mark, the argument can be set once using formatdown_options(),

formatdown_options(decimal_mark = ",")

Using the same code as above to format the metals data yields,

Table 2: Changing the decimal mark

To return to the default values,

formatdown_options(reset = TRUE)

Installation

Install from CRAN.

install.packages("formatdown")

The development version can be installed from GitHub. I suggest using the “pak” package:

pak::pkg_install("graphdr/formatdown")

Requirements

• R (>= 3.5.0)
• data.table (>= 1.9.8)

Contributing

To provide feedback or report a bug,

• Use the GitHub Issues page.

To contribute to formatdown,

• Please clone this repo locally.
• Commit your contribution on a separate branch.
• Submit a pull request

Participation in this open source project is subject to a Code of Conduct.

Software credits

• R and RStudio for the working environment
• rmarkdown and knitr for authoring tools
• data.table for its programmable syntax
• units for handling physical units
• wrapr, checkmate, and tinytest for programming tools
• devtools and pkgdown for package building