error.circles: Two way plots of means, error bars, and sample sizes

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

Two way plots of means, error bars, and sample sizes

Description

Given a matrix or data frame, data, find statistics based upon a grouping variable and then plot x and y means with error bars for each value of the grouping variable. If the data are paired (e.g. by gender), then plot means and error bars for the two groups on all variables.

Usage

errorCircles(x, y, data, ydata = NULL, group=NULL, paired = FALSE, labels = NULL, 
main = NULL, xlim = NULL, ylim = NULL, xlab = NULL, ylab = NULL,add=FALSE, pos = NULL,
 offset = 1, arrow.len = 0.2, alpha = 0.05, sd = FALSE, bars = TRUE, circles = TRUE,
 colors=NULL,col.arrows=NULL,col.text=NULL,circle.size=1, ...)

Arguments

x	The x variable (by name or number) to plot
y	The y variable (name or number) to plot
data	The matrix or data.frame to use for the x data
ydata	If plotting data from two data.frames, then the y variable of the ydata frame will be used.
group	If specified, then statsBy is called first to find the statistics by group
paired	If TRUE, plot all x and y variables for the two values of the grouping variable.
labels	Variable names
main	Main title for plot
xlim	xlim values if desired– defaults to min and max mean(x) +/- 2 se
ylim	ylim values if desired – defaults to min and max mean(y) +/- 2 se
xlab	label for x axis – grouping variable 1
ylab	label for y axis – grouping variable 2
add	If TRUE, add to the prior plot
pos	Labels are located where with respect to the mean?
offset	Labels are then offset from this location
arrow.len	Arrow length
alpha	alpha level of error bars
sd	if sd is TRUE, then draw means +/- 1 sd)
bars	Should error.bars be drawn for both x and y
circles	Should circles representing the relative sample sizes be drawn?
colors	Plot the points using colors – default is black
col.text	What color for the text labels (defaults to colors)
col.arrows	What color should the arrows and circles be? Defaults to colors
circle.size	A scaling parameter for the error.circles. Defaults to 1, but can be adjusted downwards to make them less instrusive.
...	Other parameters for plot

Details

When visualizing the effect of an experimental manipulation or the relationship of multiple groups, it is convenient to plot their means as well as their confidence regions in a two dimensional space.

The diameter of the enclosing circle (ellipse) scales as 1/sqrt(N) * the maximum standard error of all variables. That is to say, the area of the ellipse reflects sample size.

Value

If the group variable is specified, then the statistics from statsBy are (invisibly) returned.

Note

Basically this is a combination (and improvement) of statsBy with error.crosses. Can also serve some of the functionality of error.bars.by (see the last example).

Author(s)

William Revelle

See Also

statsBy, describeBy, error.crosses

Examples

#BFI scores for males and females
errorCircles(1:25,1:25,data=bfi,group="gender",paired=TRUE,ylab="female scores",
      xlab="male scores",main="BFI scores by gender")
 abline(a=0,b=1)
#drop the circles since all samples are the same sizes
errorCircles(1:25,1:25,data=bfi,group="gender",paired=TRUE,circles=FALSE,
     ylab="female scores",xlab="male scores",main="BFI scores by gender")
 abline(a=0,b=1)
 if(require(psychTools)) {
 
 data(psychTools::affect)
colors <- c("black","red","white","blue")
films <- c("Sad","Horror","Neutral","Happy")
affect.stats <- errorCircles("EA2","TA2",data=psychTools::affect[-c(1,20)],
group="Film",labels=films,
      xlab="Energetic Arousal",ylab="Tense Arousal",ylim=c(10,22),xlim=c(8,20), 
      pch=16,cex=2,colors=colors, main ="EA and TA pre and post affective movies")
#now, use the stats from the prior run 
errorCircles("EA1","TA1",data=affect.stats,labels=films,pch=16,cex=2,colors=colors,add=TRUE)

}
#show sample size with the size of the circles
errorCircles("SATV","SATQ",sat.act,group="education")

#Can also provide error.bars.by functionality
 errorCircles(2,5,group=2,data=sat.act,circles=FALSE,pch=16,colors="blue",
      ylim= c(200,800),main="SATV by education",labels="")
 #just do the breakdown and then show the points
# errorCircles(3,5,group=3,data=sat.act,circles=FALSE,pch=16,colors="blue",
#         ylim= c(200,800),main="SATV by age",labels="",bars=FALSE)

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