Tutorial 01: Introduction to R

Q1 — Make the sum equal 10

Replace ＿ with a number so the expression evaluates to 10.

Replace the two ＿ with 2 numbers that add up to 7.

1 + 2 + 3 + 4 
1 + 2 + 3 + 4

Q2 — Create a vector

Make a vector called my_vec that contains the numbers 5, 10, 15, 20.

Use the c() function to combine numbers: c(1, 2, 3)

my_vec <- c(5, 10, 15, 20) 
my_vec <- c(5, 10, 15, 20)

Q3 — Find the average

Compute the mean of the vector c(2, 4, 6, 8, 10).
Your answer should be stored in a variable called avg_val.

Use the mean() function: mean(c(…))

avg_val <- mean(c(2, 4, 6, 8, 10)) 
avg_val <- mean(c(2, 4, 6, 8, 10))

Q4 — Draw a histogram from ToothGrowth (type the full call)

Use exactly one of these numeric columns and nothing else: len or dose

Photo by The Humble Co. on Unsplash
NotePreview

Find a preview of the ToothGrowth dataset here:

Use the hist command.

hist(ToothGrowth$len) 
hist(ToothGrowth$len)

Q5 — Draw a boxplot from ToothGrowth (type the full call)

Use exactly one of these numeric columns and nothing else: len or dose

NotePreview

Find a preview of the ToothGrowth dataset here:

Use the boxplot command.

boxplot(ToothGrowth$len) 
boxplot(ToothGrowth$len)

Q6 — Add a color to the histogram

Re-draw a histogram of ToothGrowth$len and set any bar color using the col= argument.

add col as an additional argument here and give it a color of your choice.

hist(ToothGrowth$len, col = "steelblue") 
hist(ToothGrowth$len, col = "steelblue")

Q7 — Boxplot (make it horizontal)

Draw a boxplot of ToothGrowth$dose and make it horizontal using horizontal = TRUE as an argument.

add horizontal as an argument just like col from the previous question

boxplot(ToothGrowth$dose, horizontal = TRUE) 
boxplot(ToothGrowth$dose, horizontal = TRUE)

Q8 — Load a CSV as a DataFrame

Load iris.csv into a dataframe named df.

Photo by Andrew Small on Unsplash

Use read.csv here.

df <- read.csv("iris.csv") 
df <- read.csv("iris.csv")

Q9 — Count rows in iris.csv

Count the number of rows in iris.csv and store them in the variable rows

Use nrow.

df <- read.csv("iris.csv") rows <- nrow(df) 
df <- read.csv("iris.csv")
rows <- nrow(df)

Q10 — Show column names

Print the column names from iris.csv

Use names.

df <- read.csv("iris.csv") cols <- names(df) cols 
df   <- read.csv("iris.csv")
cols <- names(df)
cols

Q11 — Print some of the data

Print the first 5 rows from iris.csv.

Use head.

df <- read.csv("iris.csv") head(df) 
df <- read.csv("iris.csv")
head(df)

Q12 — Make a histogram from iris.csv

Make a histogram of the column Sepal.Length from iris.csv.

Use hist (see Q5).

df <- read.csv("iris.csv") hist(df$Sepal.Length, col = "lightgray", main = "Sepal.Length", xlab = "cm") 
df <- read.csv("iris.csv")
hist(df$Sepal.Length, col = "lightgray", main = "Sepal.Length", xlab = "cm")

Q13 — Write a function using division

Define a function called divide_nums that takes two arguments (a and b) and returns the results of:

  1. a / b
  2. b / a

Both results should be stored in separate variables before being returned.

NoteInfo

Remember: in R, division by zero (1/0) will return Inf rather than an error.

NoteInfo

In R, lists are written with list(a, b, c). Each element can be anything: a number, a string, or even another list.

Start with: res1 <- a / b res2 <- b / a and then use the list command.

divide_nums <- function(a, b) { res1 <- a / b res2 <- b / a list(res1, res2) } 
divide_nums <- function(a, b) {
  res1 <- a / b
  res2 <- b / a
  list(res1, res2)
}