**StaTEAstics.**, and kindly contributed to R-bloggers)

Despite the fact that box plot is used almost every where and taught at undergraduate statistic classes, I recently had to re-learn the box plot in order to know how to label the outliers.

This stackoverflow post was where I found how the outliers and whiskers of the Tukey box plots are defined in R and ggplot2:

In ggplot2, what do the end of the boxplot lines represent?

and this post on how to label the outliers using base graphics.

How to label all the outliers in a boxplot

Since the use of ggplot2 is required for this task, I have written some basic hack code to label the outliers for ggplot2.

Here are the codes:

## Install the FAOSTAT package to obtain the data

if(!is.element("FAOSTAT", .packages()))

install.packages("FAOSTAT")

library(FAOSTAT)

## Download data on Cassava production

cp.lst = getFAOtoSYB(name = "cassava_production", domainCode = "QC",

itemCode = 125, elementCode = 5510)

## Use the country level data, and take only data for 2011 and remove the NA's

cp.df = cp.lst$entity[!is.na(cp.lst$entity$cassava_production) &

cp.lst$entity$Year == 2011, ]

## Merge with the country profile to obtain the country names for labelling

ccp.df = merge(cp.df, FAOcountryProfile[, c("FAOST_CODE", "ABBR_FAO_NAME")],

all.x = TRUE)

## Merge with the regional pofile to obtain the UNSD M49 macro region

## composition for multiple boxplot.

rcp.df = merge(ccp.df, FAOregionProfile[, c("FAOST_CODE", "UNSD_MACRO_REG")],

all.x = TRUE)

## Compute the quantile

qrcp.df = ddply(.data = rcp.df, .variables = .(UNSD_MACRO_REG), transform,

lQntl = quantile(cassava_production, probs = 0.25, na.rm = TRUE),

uQntl = quantile(cassava_production, probs = 0.75, na.rm = TRUE))

## Compute the lower and upper bound which defines the outlier

brcp.df = ddply(.data = qrcp.df, .variables = .(UNSD_MACRO_REG), transform,

lBound = lQntl - 1.5 * (uQntl - lQntl),

uBound = uQntl + 1.5 * (uQntl - lQntl))

## Remove the country names if it is within the bounds

with(brcp.df, {

brcp.df[cassava_production <= uBound &

cassava_production >= lBound, "ABBR_FAO_NAME"] <<- NA

})

## Plot the data

set.seed(587)

ggplot(data = brcp.df, aes(x = UNSD_MACRO_REG, y = cassava_production)) +

geom_boxplot(outlier.colour = NA) +

geom_text(aes(label = ABBR_FAO_NAME), size = 2,

position = position_jitter(width = 0.1)) +

labs(x = NULL, y = NULL, title = "Production of Cassava by region")

Here is the final product, to avoid over-plotting of texts I have used *position_jitter.* Which is not an elegant solution but I just can not find any algorithm that works well in general.

**leave a comment**for the author, please follow the link and comment on his blog:

**StaTEAstics.**.

R-bloggers.com offers

**daily e-mail updates**about R news and tutorials on topics such as: visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, git, hadoop, Web Scraping) statistics (regression, PCA, time series, trading) and more...