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README.md

pillar

Lifecycle: maturing R build status Coverage status CRAN status

pillar provides tools for styling columns of data, artfully using colour and unicode characters to guide the eye.

Installation

# pillar is installed if you install the tidyverse package:
install.packages("tidyverse")

# Alternatively, install just pillar:
install.packages("pillar")

# Or the the development version from GitHub:
# install.packages("devtools")
devtools::install_github("r-lib/pillar")

Usage

pillar is a developer-facing package that is not designed for end-users but will eventually be incorporated in packages like tibble.

library(pillar)

x <- 123456789 * (10 ^ c(-3, -5, NA, -8, -10))
pillar(x)
#>       <dbl>
#> 123457.    
#>   1235.    
#>     NA     
#>      1.23  
#>      0.0123

If you render this in a console that supports colour, you’ll see something that looks like this:

Extending

The primary user of this package is tibble, which lets pillar do all the formatting work. Packages that implement a data type to be used in a tibble column can add color with only a few changes:

  1. Implement the pillar_shaft() method for your data type.
  2. Add pillar to Suggests and implement dynamic method registration using vctrs::s3_register().
    • If you don’t mind the dependency, you can also add it to Imports, and import the methods you override with a regular NAMESPACE import.

tidyverse/hms#43 shows the changes that were necessary to add colored output for the hms package:

  • pillar.R for the actual implementation (old name colformat.R)
  • DESCRIPTION for the dependency
  • zzz.R for the dynamic method registration

Some more detail is given below.

Implementing pillar_shaft.your_class_name()

This method accepts a vector of arbitrary length and is expected to return an S3 object with the following properties:

  • It has an attribute "width"
  • It can have an attribute "min_width", if missing, "width" is used
  • It must implement a method format(x, width, ...) that can be called with any value between min_width and width
    • This method must return an object that inherits from character and has attributes "align" (with supported values "left", "right", and "center") and "width"

The function new_pillar_shaft() returns such an object, and also correctly formats NA values. In many cases, the implementation of pillar_shaft.your_class_name() will format the data as a character vector (using color for emphasis) and simply call new_pillar_shaft(). See pillar_shaft.numeric() for a code that allows changing the display depending on the available width.

Useful helpers

Inspirations

  • TextPlots for use of Braille characters

  • spark for use of block characters.

The earliest use of unicode characters to generate sparklines appears to be from 2009.

Exercising these ideas to their fullest requires a font with good support for block drawing characters. PragamataPro is one such font.


Code of Conduct

Please note that the pillar project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.

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