This data set consistst of four continuous characters collected for three species of Iris. The data were assembled by Anderson (1935) and famously analysed by Fisher (1936). It is a nice dataset because it is reasonably small. This makes it easy to visualize. It also makes it a good daata set when trying to learn new analyses, particularly when the data set intende to be analysed is much larger. It is also a part of R so most intallations should have it. It can be loaded as follows.

data("iris")

More information can be found using ?iris.

We can visualize this data using histograms.

library(ggplot2)
library(reshape2)
iris2 <- melt(iris)

## Using Species as id variables

p <- ggplot(iris2, aes(x=value, fill = Species))
p <- p + geom_histogram(binwidth = 0.2, alpha=.5)
p <- p + facet_grid(. ~ variable, scales = "free")
p <- p + scale_fill_manual(values=c("#66c2a5", "#fc8d62", "#8da0cb"))
p <- p + xlab("Length")
p <- p + ylab("Count")
p <- p + theme_bw()

p

An alternative perspective would be violin plots.

p <- ggplot(iris2, aes(x=Species, y=value, fill = Species))
p <- p + geom_violin()
p <- p + scale_fill_manual(values=c("#66c2a5", "#fc8d62", "#8da0cb"))
p <- p + facet_grid(. ~ variable)
p <- p + xlab("")
p <- p + ylab("Length")
p <- p + theme_bw()

p