ellipse: plotcorr – R documentation

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plotcorr

Plot correlation matrix ellipses

Description

This function plots a correlation matrix using ellipse-shaped glyphs for each entry. The ellipse represents a level curve of the density of a bivariate normal with the matching correlation.

Usage

plotcorr(corr, outline = TRUE, col = 'grey', numbers = FALSE, 
         type = c("full","lower","upper"),
	       diag = (type == "full"), bty = "n", axes = FALSE,
	       xlab = "", ylab = "", asp = 1,
	       cex.lab = par("cex.lab"), cex = 0.75*par("cex"),
	       mar = 0.1 + c(2,2,4,2), ...)

Arguments

`corr`	A matrix containing entries between `-1` and `1` to be plotted as correlations.
`outline`	Whether the ellipses should be outlined in the default colour.
`col`	Which colour(s) to use to fill the ellipses.
`numbers`	Whether to plot numerical correlations in place of ellipses. If numbers is `TRUE`, then the correlations will be rounded to a single decimal place and placed on the plot.
`type`	Character. Plot `"full"` matrix or just `"upper"` or `"lower"` triangular part of it.
`diag`	Logical. Plot diagonal elements or not.
`bty, axes, xlab, ylab, asp, mar, cex.lab, ...`	Graphical parameters which will be passed to `plot` when plotting.
`cex`	Graphical parameter which will be passed to `text` when plotting.

Details

The ellipses being plotted will be tangent to a unit character square, with the shape chosen to match the required correlation. If numbers = FALSE, the col vector will be recycled to colour each of the ellipses; if TRUE, it will be ignored.

Author(s)

Duncan Murdoch; Gregor Gorjanc suggested the type and diag options.

References

Murdoch, D.J. and Chow, E.D. (1996). A graphical display of large correlation matrices. The American Statistician 50, 178-180.

Examples

save.par <- par(ask = interactive())

# Plot the correlation matrix for the mtcars data full model fit 
data(mtcars)
fit <- lm(mpg ~ ., mtcars)
plotcorr(summary(fit, correlation = TRUE)$correlation)

# Plot a second figure with numbers in place of the
# ellipses
plotcorr(summary(fit, correlation = TRUE)$correlation, numbers = TRUE)

# Colour the ellipses to emphasize the differences.  The color range
# is based on RColorBrewer's Reds and Blues (suggested by Gregor Gorjanc)

corr.mtcars <- cor(mtcars)
ord <- order(corr.mtcars[1,])
xc <- corr.mtcars[ord, ord]
colors <- c("#A50F15","#DE2D26","#FB6A4A","#FCAE91","#FEE5D9","white",
            "#EFF3FF","#BDD7E7","#6BAED6","#3182BD","#08519C")   
plotcorr(xc, col=colors[5*xc + 6])

plotcorr(xc, col=colors[5*xc + 6], type = "upper")
plotcorr(xc, col=colors[5*xc + 6], type = "lower", diag = TRUE)
par(save.par)

ellipse

Functions for Drawing Ellipses and Ellipse-Like Confidence Regions

v0.4.2

GPL (>= 2)

Authors

Duncan Murdoch <murdoch@stats.uwo.ca> and E. D. Chow (porting to R by Jesus M. Frias Celayeta <iosu@bureau.ucc.ie>)

Initial release