I need to build a boxplot without any axes and add it to the current plot (ROC curve), but I need to add more text information to the boxplot: the labels for min and max. Current line of code is below (current graph also).

Thanks a lot for assistance.

boxplot(data, horizontal = TRUE, range = 0, axes=FALSE, col = "grey", add = TRUE)

The other solution is add the line from 0 to 1 (instead of x-axis), but I want it to go through the central line...for example like this graphic

enter image description here


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I think you will find this produces something like your hand-drawn diagram.

data    <- c(0.4, 0.7, 0.75, 0.82, 0.9)
endaxis <- c(0, 1)  # endpoints of axis
datamm  <- c(min(data), max(data))
boxplot(data, horizontal = TRUE, range = 0, ylim = endaxis,
                    axes = FALSE, col = "grey", add = FALSE)
arrows(endaxis, 1,  datamm, 1,  code = 1, angle = 90, length = 0.1)
valuelabels <- c(endaxis[1], round(fivenum(data)[2], digits = 2) ,
                 round(fivenum(data)[4], digits = 2), endaxis[2]  ) 
text(x = valuelabels, y = c(1.05, 1.25, 1.25, 1.05), labels = valuelabels)

R boxplot with value labels

There are probably better ways of doing it. You may need to adapt it to fit your ROC plot, including changing add = FALSE

  • 1
    $\begingroup$ Well, your response seems more close to what was asked by the OP (so I've +1). However, I feel like this isn't a boxplot anymore, or at least it loose its interest in spotting possible outlying value. Of note, you can customize a little bit more the boxplot (see the pars arguments to reduce its aspect ratio (boxwex) and the size of the whiskers (staplewex)). $\endgroup$ – chl Mar 13 '11 at 9:08

Try something like this for a standalone version:

bxp <- boxplot(rnorm(100), horizontal=TRUE, axes=FALSE)
mtext(c("Min","Max"), side=3, at=bxp$stats[c(1,5)], line=-3)

Note that you can get some information when calling boxplot, in particular the "five numbers".

If you want it to be superimposed onto another graphic, use add=T but replace mtext by text; you will need to set a $y$ value (which depend on the way you plot the other graphic).

A more complete example was given by John Maindonald (code should be on his website):

enter image description here


Fully customizable ggplot2 boxplot...

data <- data.frame(value=rnorm(100,mean = 0.5, sd = 0.2),group=0)
metaData <- ddply(data,~group,summarise,
bps <- boxplot.stats(data$value,coef=1.5) 
metaData$min <- bps$stats[1] #lower wisker
metaData$max <- bps$stats[5] #upper wisker
metaData$Q1 <- bps$stats[2] # 1st Quartile
metaData$Q3 <- bps$stats[4] # 3rd Quartile

#adding outliers
out <- data.frame() #initialising storage for outliers
if(length(bps$out) > 0){
	for(n in 1:length(bps$out)){
		pt <-data.frame(value=bps$out[n],group=0) 
#adding labels
labels <-data.frame(value=metaData$max, label="Upper bound")
labels <-rbind(labels,data.frame(value=metaData$min, label="Lower bound"))
labels <-rbind(labels,data.frame(value=metaData$median, label="Median"))
labels <-rbind(labels,data.frame(value=metaData$Q1, label="First quartile"))
labels <-rbind(labels,data.frame(value=metaData$Q3, label="Third quartile"))

p <- ggplot(metaData,aes(x=group,y=mean))
p <- p + geom_segment(aes(x=c(0.1,0,0.1),y=c(0,0,1),xend=c(0,0,-0.1),yend=c(0,1,1)))
p <- p + geom_text(aes(y=c(0,1),label=c(0,1),x=0.2))
p <- p + geom_errorbar(aes(ymin=min,ymax=max),linetype = 1,width = 0.5) #main range
p <- p + geom_linerange(aes(ymin=min,ymax=max),linetype = 1,width = 0, color="white")# white line range
p <- p + geom_linerange(aes(ymin=min,ymax=max),linetype = 2)    #main range dotted
p <- p + geom_crossbar(aes(y=median,,ymin=Q1,ymax=Q3),linetype = 1,fill='white') #box
if(length(out) >0) p <- p + geom_point(data=out,aes(x=group,y=value),shape=4) # drawning outliers if any
p <- p + scale_x_discrete(breaks=c(0))
p <- p + scale_y_continuous(name= "Value")
p <- p + geom_text(data=labels,aes(x=0.5,y=value,label=round(value,2)),colour="black",angle=0,hjust=0.5, vjust=0.5,size=3)

p <- p + opts(panel.background = theme_rect(fill = "white",colour = NA)) 
p <- p + opts(panel.grid.minor = theme_blank(), panel.grid.major = theme_blank())
p <- p + opts(axis.title.x=theme_blank())
p <- p + opts(axis.text.x = theme_blank())
p <- p + opts(axis.title.y=theme_blank())
p <- p + opts(axis.text.y = theme_blank())

p + coord_flip()


enter image description here

...code maybe a bit ugly but works the right way.


Here is mine implementation of your solutions. I've decided not to map the mean value, there is not to much space left. Also the line from 0 to 1 seems odd. Thank's a lot everyone.

data <- read.table("roc_average.txt")
bxp <- boxplot(data, horizontal = TRUE, range = 0, axes = FALSE, col = "grey", add = TRUE, at = 0.2, varwidth=FALSE, boxwex=0.3)
valuelabels <- c(round(fivenum(data)[2], digits = 2), round(fivenum(data)[4], digits = 2))
text(x = valuelabels, y = c(0.35, 0.35), labels = valuelabels, font = 2)
mtext(c(min(round(data, digits = 2)),max(round(data, digits = 2))), side=1, at=bxp$stats[c(1,5)], line=-3, font = 2)

roc curve with boxplot

  • $\begingroup$ The boxplot is supposed to summarize the AUC? If so, why is the min value = 0.5? $\endgroup$ – chl Mar 17 '11 at 22:22
  • $\begingroup$ yep, seems strange, because several ROC should be below 0.5. Digging up what's wrong... $\endgroup$ – Vladimir Chupakhin Mar 19 '11 at 12:39
  • $\begingroup$ That is the point I have inverted the ROC AUC for values below 0.5, so the graphics should be remade. Thanks a lot! $\endgroup$ – Vladimir Chupakhin Apr 6 '11 at 13:06
  • $\begingroup$ +1 for coming back, I'm waiting for your update. If you're working with different classifiers, you might have a look at ROCR. $\endgroup$ – chl Apr 6 '11 at 19:10
  • $\begingroup$ I did ROC curve with ROCR $\endgroup$ – Vladimir Chupakhin Apr 7 '11 at 12:56

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