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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 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):

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

Citation

To cite the cld package in publications:

citation("cld")

License

GPL-3