scatter.hist: Draw a scatter plot with associated X and Y histograms,...

In psych: Procedures for Psychological, Psychometric, and Personality Research

Draw a scatter plot with associated X and Y histograms, densities and correlation

Description

Draw a X Y scatter plot with associated X and Y histograms with estimated densities. Will also draw density plots by groups, as well as distribution ellipses by group. Partly a demonstration of the use of layout. Also includes lowess smooth or linear model slope, as well as correlation and Mahalanobis distances

Usage

scatterHist(x,y=NULL,smooth=TRUE,ab=FALSE, correl=TRUE,data=NULL, density=TRUE,means=TRUE, 
   ellipse=TRUE,digits=2,method="pearson",cex.cor=1,cex.point=1,
   title="Scatter plot + density",
   xlab=NULL,ylab=NULL,smoother=FALSE,nrpoints=0,xlab.hist=NULL,ylab.hist=NULL,grid=FALSE,
   xlim=NULL,ylim=NULL,x.breaks=11,y.breaks=11,
   x.space=0,y.space=0,freq=TRUE,x.axes=TRUE,y.axes=TRUE,size=c(1,2),
   col=c("blue","red","black"),legend=NULL,alpha=.5,pch=21, show.d=TRUE,
   x.arrow=NULL,y.arrow=NULL,d.arrow=FALSE,cex.arrow=1,...)
 
scatter.hist(x,y=NULL,smooth=TRUE,ab=FALSE, correl=TRUE,data=NULL,density=TRUE,
  means=TRUE, ellipse=TRUE,digits=2,method="pearson",cex.cor=1,cex.point=1,
  title="Scatter plot + density",
  xlab=NULL,ylab=NULL,smoother=FALSE,nrpoints=0,xlab.hist=NULL,ylab.hist=NULL,grid=FALSE,
  xlim=NULL,ylim=NULL,x.breaks=11,y.breaks=11,
  x.space=0,y.space=0,freq=TRUE,x.axes=TRUE,y.axes=TRUE,size=c(1,2),
  col=c("blue","red","black"),legend=NULL,alpha=.5,pch=21, show.d=TRUE,
   x.arrow=NULL,y.arrow=NULL,d.arrow=FALSE,cex.arrow=1,...)

Arguments

x	The X vector, or the first column of a data.frame or matrix. Can be specified using formula input.
y	The Y vector, of if X is a data.frame or matrix, the second column of X
smooth	if TRUE, then add a loess smooth to the plot
ab	if TRUE, then show the best fitting linear fit
correl	TRUE: Show the correlation
data	if using formula input, the data must be specified
density	TRUE: Show the estimated densities
means	TRUE: If TRUE, show the means for the distributions.
ellipse	TRUE: draw 1 and 2 sigma ellipses and smooth
digits	How many digits to use if showing the correlation
method	Which method to use for correlation ("pearson","spearman","kendall") defaults to "pearson"
smoother	if TRUE, use smoothScatter instead of plot. Nice for large N.
nrpoints	If using smoothScatter, show nrpoints as dots. Defaults to 0
grid	If TRUE, show a grid for the scatter plot.
cex.cor	Adjustment for the size of the correlation
cex.point	Adjustment for the size of the data points
xlab	Label for the x axis
ylab	Label for the y axis
xlim	Allow specification for limits of x axis, although this seems to just work for the scatter plots.
ylim	Allow specification for limits of y axis
x.breaks	Number of breaks to suggest to the x axis histogram.
y.breaks	Number of breaks to suggest to the y axis histogram.
x.space	space between bars
y.space	Space between y bars
freq	Show frequency counts, otherwise show density counts
x.axes	Show the x axis for the x histogram
y.axes	Show the y axis for the y histogram
size	The sizes of the ellipses (in sd units). Defaults to 1,2
col	Colors to use when showing groups
alpha	Amount of transparency in the density plots
legend	Where to put a legend c("topleft","topright","top","left","right")
pch	Base plot character (each group is one more)
xlab.hist	Not currently available
ylab.hist	Label for y axis histogram. Not currently available.
title	An optional title
show.d	If TRUE, show the distances between the groups
d.arrow	If TRUE, draw an arrow between the two centroids
x.arrow	optional lable for the arrow connecting the two groups for the x axis
y.arrow	optional lable for the arrow connecting the two groups for the y axis
cex.arrow	cex control for the label size of the arrows.
...	Other parameters for graphics

Details

Just a straightforward application of layout and barplot, with some tricks taken from pairs.panels. The various options allow for correlation ellipses (1 and 2 sigma from the mean), lowess smooths, linear fits, density curves on the histograms, and the value of the correlation. ellipse = TRUE implies smooth = TRUE. The grid option provides a background grid to the scatterplot.

If using grouping variables, will draw ellipses (defaults to 1 sd) around each centroid. This is useful when demonstrating Mahalanobis distances.

Formula input allows specification of grouping variables as well. )

For plotting data for two groups, Mahalobnis differences between the groups may be shown by drawing an arrow between the two centroids. This is a bit messy and it is useful to use pch="." in this case.

Note

Originally adapted from Addicted to R example 78. Modified following some nice suggestions from Jared Smith. Substantial revisions in 2021 to allow for a clearer demonstration of group differences.

Author(s)

William Revelle

See Also

pairs.panels for multiple plots, multi.hist for multiple histograms and histBy for single variables with multiple groups. Perhaps the best example is found in the psychTools::GERAS data set.

Examples

data(sat.act)
with(sat.act,scatterHist(SATV,SATQ))
scatterHist(SATV ~ SATQ,data=sat.act)  #formula input

#or for something a bit more splashy
scatter.hist(sat.act[5:6],pch=(19+sat.act$gender),col=c("blue","red")[sat.act$gender],grid=TRUE)
#better yet
scatterHist(SATV ~ SATQ + gender,data=sat.act) #formula input with a grouping variable

psych documentation built on June 27, 2024, 5:07 p.m.