Plot a Web of Connected Points

Displays a symmetric matrix (typically a correlation matrix) as a network diagram: variables are placed equidistantly around a circle, and connecting lines between each pair are drawn with width proportional to the absolute value of the matrix entry and color indicating its sign.

Usage

plotWeb(
  m,
  main = NULL,
  dist = 0.5,
  col = hcol("red", "blue"),
  lty = NULL,
  lwd = NULL,
  labels = TRUE,
  points = list(pch = 21, cex = 2, col = "black", bg = "darkgrey"),
  legend = TRUE,
  stamp = .useTheme,
  ...
)

Arguments

m

a symmetric numeric matrix (e.g. a correlation matrix).

main

main title of the plot. NULL (default) produces no title.

dist

distance of node labels from the outer circle. Default 0.5.

col

two colors for the connecting lines: the first is used for negative values, the second for positive values. .useTheme (default) resolves to getTheme()$twin - consistent with the sign-based coloring in plotCor().

lty

line type for the connecting lines. NULL (default) inherits from par("lty").

lwd

line widths for the connecting lines. NULL (default) scales widths linearly between 0.5 and 10 in proportion to the absolute matrix values.

labels

controls node labels around the circle. TRUE (default) draws labels using colnames(m) with default styling. FALSE/NA/NULL suppresses labels. A named list overrides individual settings:

labels

character vector of label texts; defaults to colnames(m)

las

orientation: 1 horizontal (default), 2 radial, 3 vertical

adj

label adjustment (0/0.5/1); NULL (default) chooses automatically based on position around the circle

cex

character expansion; default 1.0

points

controls the node point symbols. The default (list(pch=21, cex=2, col="black", bg="darkgrey")) draws prominent filled circles, larger than the generic data-point default, since nodes represent variables rather than observations. FALSE/NA/NULL suppresses the points. A named list overrides individual elements (pch, cex, col, bg).

legend

controls the legend. TRUE (default) draws a legend showing the line widths and colors for the minimum/maximum positive and negative values. FALSE/NA suppresses it. A named list overrides arguments forwarded to graphics::legend().

stamp

controls the corner stamp. .useTheme (default) resolves to getTheme()$stamp. TRUE/FALSE/ NULL, a string, or a named list for stamp().

...

further graphical parameters passed to graphics::par() and to the internal canvas() call.

Value

Invisibly returns a list of x/y coordinates of the node points, useful for adding further annotations to the plot.

Details

The function uses the lower triangular matrix of m; when overriding lwd or col manually, values must be supplied in the same order as m[lower.tri(m)].

See also

plotCor(), theme

Other plot.special: plotBinaryTree(), plotCirc(), plotLift(), plotMiss(), plotPolar(), plotPropCI(), plotTernary(), plotTimeSeries(), plotTreemap()

Examples

m <- cor(swiss)
plotWeb(m, main = "Swiss correlation")


# custom labels (abbreviations)
plotWeb(m, labels = list(labels = abbreviate(colnames(m), 4), cex = 0.9))


# show only significant correlations
p <- outer(
  (vars <- colnames(mtcars)), vars,
  Vectorize(function(v1, v2)
    cor.test(mtcars[[v1]], mtcars[[v2]])$p.value)
)
dimnames(p) <- list(vars, vars)
m2 <- cor(mtcars)
m2[p > 0.05] <- NA
plotWeb(m2, labels = list(las = 2))