Plotting Basics

• xy Plot
• Pairs
• Histogram
• Box Plot

xy Plot

The general formula is y ~ x. This is useful annotation as it is used in the lm() and anova() functions as well.

plot(Sepal.Length ~ Sepal.Width, data = iris)

Exercise

Use the help file to:

• Make the points triangles rather than circles.
• Make the lines dashed.
• Create a title. Color it blue.
• Add a legend.
• Make a horizontal line

We can add on linear regressions too:

model.iris <- lm(Sepal.Length ~ Sepal.Width, data = iris)
abline(model.iris)

Pairs

pairs(iris)

Discuss: What is the output of this function?

Histogram

> hist(iris$Petal.Length)

Exercise:

• Log-transform the histogram

Box plot

This is where factors come in handy!

boxplot(Petal.Width ~ Species, data = iris)

# reorder so that it the opposite way
iris$Species <- factor(iris$Species, levels = c("virginica", "versicolor", "setosa"))

Exercise:

What is the spread of petal widths per species? What is the median petal width per species?