8.8 Exercise 2B - review scatter plots before the second day

For this exercise, we will use a built-in dataset iris: this dataset shows data from several flower species.

  1. Explore dataset: check dim(iris); head(iris); tail(iris)
correction 
dim(iris)
## [1] 150   5
head(iris)
##   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1          5.1         3.5          1.4         0.2  setosa
## 2          4.9         3.0          1.4         0.2  setosa
## 3          4.7         3.2          1.3         0.2  setosa
## 4          4.6         3.1          1.5         0.2  setosa
## 5          5.0         3.6          1.4         0.2  setosa
## 6          5.4         3.9          1.7         0.4  setosa
tail(iris)
##     Sepal.Length Sepal.Width Petal.Length Petal.Width   Species
## 145          6.7         3.3          5.7         2.5 virginica
## 146          6.7         3.0          5.2         2.3 virginica
## 147          6.3         2.5          5.0         1.9 virginica
## 148          6.5         3.0          5.2         2.0 virginica
## 149          6.2         3.4          5.4         2.3 virginica
## 150          5.9         3.0          5.1         1.8 virginica


  1. Create a scatter plot of sepal length (x-axis) versus petal length (y-axis)
correction 
ggplot(data=iris, mapping=aes(x=Sepal.Length, y=Petal.Length)) +
  geom_point()


  1. Conditionally color points per species
correction 
ggplot(data=iris, mapping=aes(x=Sepal.Length, y=Petal.Length, color=Species)) +
  geom_point()



  1. Add a regression line (or regression lines) to the plot
correction 
ggplot(data=iris, mapping=aes(x=Sepal.Length, y=Petal.Length, color=Species)) +
  geom_point() +
  geom_smooth()


  1. Change the plot’s default background, add a title, and save plot to a file (either using RStudio interface, or with ggsave() function)
correction 
psepal <- ggplot(data=iris, mapping=aes(x=Sepal.Length, y=Petal.Length, color=Species)) +
  geom_point() +
  geom_smooth() +
  theme_minimal(base_size = 16) +
  ggtitle("Sepal length versus Petal length")

plot(psepal)

# save as PNG file
ggsave(filename="sepal_scatter.png", plot=psepal, 
       device="png")