Assignment 2 - Practicing with ggplot2

Learning Outcomes

• Practice using ggplot2 to create data visualizations.
• Identify the uses of different types of visualizations.
• Explain the biological or environmental significance of a data visualization.

Grading note

• Problem 1 is worth 5 points
• Problem 2 is worth 5 points

Problem 1 - Plotting relationships between variables

In section 03 we learned to use ggplot2 to make an x-y scatter plot comparing Sepal.Length and Petal.Length in the iris data set.

Recall that you must first install ggplot2 if you have not done so already. ONLY DO THIS IF YOU HAVE NOT ALREADY INSTALLED GGPLOT 2:

install.packages("ggplot2")

Then load it into your environment:

library(ggplot2)

The code to create one of the plots from section 03 looks like this:

data(iris)

ggplot(data = iris, aes( x = Sepal.Length, y = Petal.Length, colour = Species )) + 
  geom_point()

We also learned that you can add the term geom_smoth(method = "lm") to add linear regression lines onto your plot, as such:

# You will modify this code, as per description below
ggplot(data = iris, aes( x = Sepal.Length, y = Petal.Length, colour = Species )) + 
  geom_point() +
  geom_smooth(method = "lm")

## `geom_smooth()` using formula = 'y ~ x'

Use the code above, but replace Petal.Length with Sepal.Width. Make a new x-y scatter plot with linear regression lines. Describe how having separate lines for each species versus one line for all of the data combined influences your interpretations of these data, and specificially the relationship between Sepal.Length and Sepal.Width.

Hint: You should make another plot where you do not include any color arguments to see what happens. That is, a plot where you ignore the species identifications.

Put your written answer to the question here.

Problem 2 - Histograms

Below is a code chunk to create a histogram of petal length values using the iris data set.

ggplot() +
  geom_histogram(data = iris, aes(x = Petal.Length, fill = Species), 
                 position = "dodge") +
  theme_bw() 

Modify this code to make a histogram for Sepal.Length instead.

# Put your code here.

What differences do you notice about the values, as presented in these histograms, for petal length versus sepal length?

Put your written answer to the question above, here.