2.Violin plots

2.1 Basic violin plot

df$cyl <- as.factor(df$cyl)
head(df)

##                    mpg cyl    wt
## Mazda RX4         21.0   6 2.620
## Mazda RX4 Wag     21.0   6 2.875
## Datsun 710        22.8   4 2.320
## Hornet 4 Drive    21.4   6 3.215
## Hornet Sportabout 18.7   8 3.440
## Valiant           18.1   6 3.460

ggplot(df, aes(x=cyl, y=mpg)) +
    geom_violin(trim=FALSE) +
    labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg")

2.2 Add summary statistics on a violin plot

2.2.1 Add median and quartile

ggplot(df, aes(x=cyl, y=mpg)) + 
  geom_violin(trim=FALSE) +
  labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg") +
  stat_summary(fun.y=mean, geom="point", shape=23, size=2, color="red")
#or
ggplot(df, aes(x=cyl, y=mpg)) + 
  geom_violin(trim=FALSE) +
  labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg") +
  geom_boxplot(width=0.1)

2.2.2 Add mean and standard deviation

ggplot(df, aes(x=cyl, y=mpg)) + 
  geom_violin(trim=FALSE) +
  labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg") +
  stat_summary(fun.data="mean_sdl", fun.args = list(mult = 1), geom="crossbar", width=0.1 )
#or
ggplot(df, aes(x=cyl, y=mpg)) + 
  geom_violin(trim=FALSE) +
  labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg") +
  stat_summary(fun.data=mean_sdl, fun.args = list(mult = 1), geom="pointrange", color="red")

2.3 Change violin plot fill colors

ggplot(df, aes(x=cyl, y=mpg, fill=cyl)) + 
  geom_violin(trim=FALSE) +
  geom_boxplot(width=0.1, fill="white") +
  labs(title="Plot of mpg per cyl", x="Cyl", y = "Mpg") +
  scale_fill_brewer(palette="Blues") + 
  theme_classic()

Reference: http://www.sthda.com/english/wiki/ggplot2-violin-plot-quick-start-guide-r-software-and-data-visualization