corrgram2: Draw a correlogram using 'grid' graphics

In corrgram: Plot a Correlogram

Draw a correlogram using 'grid' graphics

Description

'corrgram2()' produces a correlogram using grid graphics. The off-diagonal cells can be shaded or filled with custom panel functions to show the correlation structure of a data matrix or correlation matrix.

Usage

corrgram2(
  x,
  type = NULL,
  order = FALSE,
  labels,
  panel = grid_panel.shade,
  ...,
  lower.panel = panel,
  upper.panel = panel,
  diag.panel = NULL,
  text.panel = grid_text.panel,
  label.pos = c(0.5, 0.5),
  label.srt = 0,
  cex.labels = "fit",
  dir = "left",
  legend = FALSE,
  col.regions = colorRampPalette(c("red", "salmon", "white", "royalblue", "navy")),
  cor.method = "pearson",
  title = NULL,
  abs = FALSE
)

Arguments

x	A data frame or matrix with one observation per row, or a correlation matrix.
type	Use 'data' or 'cor'/'corr' to explicitly specify whether 'x' is raw data or a correlation matrix. Usually this is inferred.
order	Should variables be reordered? Use 'FALSE' for no reordering, 'TRUE' or '"PC"' for PCA-based angular ordering, or '"seriation"' for optimal seriation via the 'cba' package.
labels	Labels to use on the diagonal instead of column names.
panel	Default panel function used for both 'lower.panel' and 'upper.panel'.
...	Additional arguments passed to the panel functions.
lower.panel, upper.panel	Separate panel functions used below and above the diagonal.
diag.panel	Optional panel function used on the diagonal before drawing diagonal labels.
text.panel	Included for API compatibility with [corrgram()]. Diagonal labels are currently drawn with [grid_text.panel()].
label.pos	Horizontal and vertical placement of the diagonal label.
label.srt	Rotation for diagonal labels.
cex.labels	Label size for diagonal labels. Use '"fit"' to size labels to the panel width.
dir	Direction of the main diagonal. Use '"left"' or '"\"' for a descending diagonal, and '"right"' or '"/"' for an ascending diagonal.
legend	If 'TRUE', draw a legend for the color scale.
col.regions	A function returning a vector of colors.
cor.method	Correlation method passed to panel functions. Default is '"pearson"'.
title	Optional title drawn above the correlogram.
abs	Logical; if 'TRUE', use absolute correlations for variable reordering.

Details

This function is a grid-graphics variant of [corrgram()]. It accepts either a data matrix/data frame with one observation per row or a correlation matrix. When raw data are supplied, correlations are computed with 'use = "pairwise.complete.obs"'.

Variable reordering can be used to improve the display by placing related variables near each other. 'order = TRUE' and 'order = "PC"' use the PCA-based angular ordering described by Friendly (2002). 'order = "seriation"' uses 'cba::seriation(..., method = "Optimal")' and requires the 'cba' package.

Value

Invisibly returns 'NULL'.

References

Friendly, Michael. 2002. Corrgrams: Exploratory Displays for Correlation Matrices. *The American Statistician*, 56, 316–324. http://datavis.ca/papers/corrgram.pdf

D. J. Murdoch and E. D. Chow. 1996. A Graphical Display of Large Correlation Matrices. The American Statistician, 50, 178-180.

Examples

# Draw a grid-based correlogram from data
vars6 <- setdiff(colnames(auto), c("Model", "Origin"))
corrgram2(auto[vars6], order = TRUE,
    lower.panel = grid_panel.shade,
    upper.panel = grid_panel.pie)

# 'vote' is a correlation matrix
corrgram2(vote, order = TRUE, upper.panel = grid_panel.conf)

corrgram documentation built on Sept. 3, 2026, 1:06 a.m.