errorCircles {psych}

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)