R Syntax and Data Structures Answer Key

Exercise 1

1. Try to create a vector of numeric and character values by combining the two vectors that we just created (glengths and species). Assign this combined vector to a new variable called combined. Hint: you will need to use the combine c() function to do this.

# Assign the vector of glengths and species to combined
combined <- c(glengths, species)

2. Print the combined vector in the console, what looks different compared to the original vectors?

# Print the combined vector to the console
combined

[1] "4.6"   "3000"  "50000" "ecoli" "human" "corn" 

glengths has been coerced into being a character vector.

Exercise 2

Let’s say that in our experimental analyses, we are working with three different sets of cells: normal, cells knocked out for geneA (a very exciting gene), and cells overexpressing geneA. We have three replicates for each celltype.

1. Create a vector named samplegroup with nine elements: 3 control (“CTL”) values, 3 knock-out (“KO”) values, and 3 over-expressing (“OE”) values.

# Create the samplegroup vector with 3 CTL, 3 KO and 3 OE
samplegroup <- c("CTL", "CTL", "CTL", "KO", "KO", "KO", "OE", "OE", "OE")

2. Turn samplegroup into a factor data structure.

# Convert samplegroup into a factor and re-assign it to samplegroup
samplegroup <- factor(samplegroup)

Exercise 3

Create a data frame called favorite_books with the following vectors as columns:

# Create a character vector containing book names and assign it to titles
titles <- c("Catch-22", "Pride and Prejudice", "Nineteen Eighty Four")
# Create a numeric vector containing page numbers and assign it to pages
pages <- c(453, 432, 328)

# Create a data frame of titles and pages
favorite_books <- data.frame(titles, pages)

Exercise 4

Create a list called list2 containing species, glengths, and number.

# Create a list called list2 composed of species, glengths and number
list2 <- list(species, glengths, number)