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Draw a correlogram using `grid` graphics

Source: R/corrgram_grid.R
corrgram2.Rd

`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.

Value

Invisibly returns `NULL`.

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.

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)