How to modify whiskers of a boxplot in ggplot2?

Problem

We want to modify the colour of the whiskers in a boxplot using ggplot2. In our example, the default colour (black) to red.

library(ggplot2)
p <- ggplot(mtcars, aes(factor(cyl), mpg, fill = factor(am)))
p + geom_boxplot()

Solution

• Option 1

We plot error bars in red and then superimpose the boxplots in black.

library(ggplot)
p + stat_boxplot(
  geom = "errorbar",
  colour = "red",
  width = 0,
  position = position_dodge(0.75)
) +
  geom_boxplot(coef = 0, outlier.shape = NA)


• Option 2

We superimpose two boxplots on top of each other. The first one with red borders and the secong one without whiskers in black.

p + geom_boxplot(color="red") + 
  geom_boxplot(aes(ymin=..lower.., ymax=..upper..)) 

References

• Box and whiskers plot.
• stackoverflow

How to remove whiskers in a boxplot in ggplot2

Problem

We want to remove whiskers in a boxplot created with ggplot2.

library(ggplot2)
p <- ggplot(mtcars, aes(factor(cyl), mpg))
p + geom_boxplot()

Solution

We specify coef = 0, overwriting the default value (coef = 1.5).

p <- ggplot(mtcars, aes(factor(cyl), mpg))
p + geom_boxplot(outlier.size = 0, coef = 0)

Related posts

• How to remove whiskers in a boxplot with the R Base Package

How to remove whiskers in a boxplot with the R Base Package

Problem

We want to remove whiskers in a boxplot created with the R base package.

boxplot(mpg ~ cyl, data = mtcars)

Solution

We pass the arguments: whisklty = 0, staplelty = 0.

whisklty - to control the whisker line type (default: "dashed").
staplelty - to control the staple (= end of whisker) line type.

boxplot(mpg ~ cyl, data = mtcars, whisklty = 0, staplelty = 0)

Related posts

• How to remove whiskers in a boxplot in ggplot2

How to change the width of error bars in ggplot2

Problem

We want to change the width of the error bars in a boxplot created with ggplot2. We use stat_boxplot(geom ='errorbar') to add error bars.

library(ggplot2)
ggplot(iris, aes(factor(Species), Sepal.Width, fill = Species)) +
    geom_boxplot() + 
    stat_boxplot(geom ='errorbar')

Solution

We use the argument width inside stat_boxplot.

library(ggplot2)
ggplot(iris, aes(factor(Species), Sepal.Width, fill = Species)) +
  geom_boxplot() + 
  stat_boxplot(geom ='errorbar', width = 0.5) 

How to annotate a boxplot in ggplot2

Problem

We want to annotate a boxplot in ggplot2. In our example we will add Tukey's five number summary (minimum, lower-hinge, median, upper-hinge, and maximum).

fivenum(iris$Sepal.Width)

[1] 2.0 2.8 3.0 3.3 4.4

library(ggplot2)
ggplot(iris, aes(factor(0), Sepal.Width)) + 
geom_boxplot() + xlab("") + scale_x_discrete(breaks = NULL)

Solution

We store Tukey's five number summary as a data frame, and then pass it as the argument data inside geom_text to add text to the plot.

five <- data.frame(x = rep(1, 5), five = fivenum(iris$Sepal.Width))
ggplot(iris, aes(x = 0, y = Sepal.Width)) + 
  geom_boxplot() + xlab("") + scale_x_discrete(breaks = NULL) + 
  geom_text(data = five, aes(x = 0, y = five, label = five), nudge_x = 0.5)

References

• geom_text
• geom_boxplot

How to create boxplots grouping into intervals x-axis values using R?

Problem

We want to create boxplots grouping into intervals the values of the x-axis, like in the example below.

Solution

Data

We generate random data and a sequence to create the intervals.

set.seed(12)
y <- rnorm(1000)
x <- rnorm(1000)
rng <- seq(-3, 3, 0.5)

Base

boxplot(y ~ cut(x, breaks = rng),las=2)

If we'd like to include not available data (NAs), we use the function addNA:

boxplot(y ~ addNA(cut(x, breaks = rng)), las = 2)

ggplot2

First we create data frame with the intervals.

library(ggplot2)
df <- data.frame(x = cut(x, breaks = rng), y = y)
ggplot(data = df, aes(x = x, y = y)) + geom_boxplot(aes(fill = x))

Related posts

Spanish version

References

• stackoverflow

Anotar diagrama de caja en ggplot2

Problema

Deseamos anotar el siguiente diagrama de caja en ggplot2 y añadir los 5 números de Tukey: mínimo, bigote inferior, mediana, bigote superior, máximo.

fivenum(iris$Sepal.Width)

[1] 2.0 2.8 3.0 3.3 4.4

library(ggplot2)
ggplot(iris, aes(factor(0), Sepal.Width)) + 
geom_boxplot() + xlab("") + scale_x_discrete(breaks = NULL)

Solución

Creamos el data frame five con los 5 números de Tukey que utilizamos en los argumentos de geom_text para anotar el gráfico.

five <- data.frame(x = rep(1, 5), five = fivenum(iris$Sepal.Width))
ggplot(iris, aes(x = 0, y = Sepal.Width)) + 
  geom_boxplot() + xlab("") + scale_x_discrete(breaks = NULL) + 
  geom_text(data = five, aes(x = 0, y = five, label = five), nudge_x = 0.5)

Referencias

• geom_text
• geom_boxplot

Entradas relacionadas

• Diagramas de caja con ggplot2 en R. Una introducción
• Introducción al diagrama de caja (box plot) en R
• Múltiples diagramas de caja en R
• Múltiples diagramas de caja usando la función plot en R
• Diagrama de caja con intervalos de confianza para la mediana
• Diagramas de caja de un data frame con ggplot2: una o varias columnas