cld: Compact Letter Display for Statistical Comparisons

Simplify your statistical reporting with compact letter displays

The cld package provides an easy and consistent way to create compact letter displays (CLDs) for visualizing results of pairwise statistical comparisons. Groups sharing the same letter are not significantly different from each other — a convention widely used in agricultural, biological, and statistical publications.

Why Use cld?

Key Features:

• 🔄 Universal compatibility - Works with base R, PMCMRplus, rstatix, DescTools, and custom formats
• 🎯 One function - make_cld() handles all input types automatically
• 📊 Publication-ready - Clean, professional statistical grouping labels
• 📝 Informative - Stores metadata (alpha, method, comparison counts)
• 🛠️ Well-tested - Comprehensive unit tests ensure reliability

Installation

Install the stable version from CRAN:

install.packages("cld")

Install the development version from GitHub:

# install.packages("devtools")
devtools::install_github("GegznaV/cld")

Quick Start

The cld package works with various statistical test outputs. Here’s a simple example:

library(cld)

# Run a pairwise test
test_result <- pairwise.wilcox.test(chickwts$weight, chickwts$feed, exact = FALSE)

# Generate compact letter display
make_cld(test_result)
#>      group cld spaced_cld
#>     casein   a        a__
#>  horsebean   b        _b_
#>    linseed  bc        _bc
#>   meatmeal  ac        a_c
#>    soybean   c        __c
#>  sunflower   a        a__

Interpretation:

• Groups sharing at least one letter are not significantly different (e.g., casein and sunflower both have “a”);
• Groups with no shared letters are significantly different (e.g., horsebean “b” and soybean “c”).

Supported Input Formats

The make_cld() function works seamlessly with:

Input Type	Example Packages	Function Examples
pairwise.htest	base R	pairwise.t.test(), pairwise.wilcox.test()
PMCMR / PMCMRplus	PMCMR, PMCMRplus	kwAllPairsConoverTest(), dunnTest()
data.frame (rstatix)	rstatix	games_howell_test(), tukey_hsd()
PostHocTest	DescTools	ConoverTest(), DunnettTest()
matrix	Custom	Symmetric p-value matrices
data.frame	Custom	Custom comparison data frames
formula	Custom	Formula interface for data frames

Learn More

📚 Comprehensive vignettes (also available on package website):

• vignette("cld") - Complete introduction with examples
• vignette("cld-input-formats") - Detailed examples for all input types
• vignette("cld-interpretation-guide") - How to correctly interpret CLDs
• vignette("cld-advanced-features") - Advanced features and custom parameters

Related Packages

Package	Purpose	Relationship to cld
multcompView	CLD algorithm	Used internally by cld
rcompanion	Statistical functions	Alternative CLD implementation
PMCMRplus	Post-hoc tests	Compatible input for cld
rstatix	Tidy statistics	Compatible input for cld
DescTools	Statistical tools	Compatible input for cld

Getting Help

• 📖 Function reference: ?cld::make_cld
• 📚 Package website: https://gegznav.github.io/cld/
• 🐛 Report bugs: https://github.com/GegznaV/cld/issues
• 💬 Ask questions: GitHub Discussions

Citation

To cite the cld package in publications:

citation("cld")

License

GPL-3