14.6 Histograms using qplot

• made with geom = “histogram” arguement
• very very easy to make in R with ggplot
• very very very hard to make in Excel
• You should make them all the time for you data!

14.6.1 Histograms of iris data

• This code makes a histogram of one of the iris species’ Petal.Length.
• Note that you don’t have “y =” or “x =” for a histogram!

qplot(Petal.Length,
      data = iris)

14.6.2 Histogram with colors

What does this show?

qplot(Petal.Length,
      data = iris,
      fill = Species)

14.6.3 Histogram with axes labels

qplot(Petal.Length,
      data = iris,
      fill = Species) +  
  xlab ("Sepal Length (mm)")

14.6.4 Multiple histograms: “Facets”

What does this show?

qplot(Petal.Length,
      data = iris,
      fill = Species,
      facets = Species ~.) 

Add a label to x-axis

qplot(Petal.Length,
      data = iris,
      fill = Species,
      facets = Species ~.) +  
  xlab("Sepal Length (mm)")