Homework 3

Due 2/24/24 @ 11:59 PM

Use an RMD or QMD file to create the assignment.

You must comment all your code to receive credit.

Submit the *.html file to canvas.

Problem 1

Using the vectors below, use sapply() to determine if the numbers are even or odd.

x <- 1:20

evenodd <- function(x){
  if (x %% 2 ==0){
    return("Even")
  } else {
    return("Odd")
  }
}
sapply(x, evenodd)

Problem 2

Evaluate the following function:

\[ k(j(i(h(g(f(x)))))) \]

• \(f(x)=\sin(x)\)

• \(g(x) = x^2 +5\)

• \(h(x) = \exp{2x}\)

• \(i(x) = \sin(\pi x)\)

• \(j(x) = x^2 + 5\)

• \(k(x) = \sqrt x\)

You are not allowed to store values, but you may create and store functions.

4 |> sin() |> 
  (\(x) x^2 + 5)() |> 
  (\(x) exp(2*x))() |> 
  sinpi() |> 
  (\(x) x^2 + 5)() |> 
  sqrt()  

Problem 3

From the penguins data set from palmerpenguins package, create a new variable indicating if the penguin’s flipper length (flipper_length_mm) is greater than the average flipper length. Afterwards, group by the new variable and find the mean body_mass_g.

library(tidyverse)
library(palmerpenguins)

penguins |> drop_na() |> 
  mutate(hilo = ifelse(flipper_length_mm > mean(flipper_length_mm),
                       "Flipper Length greater than mean",
                       "Flipper Length less than mean")) |>
  group_by(hilo) |> 
  summarise(mean = mean(body_mass_g))

Problem 4

From the penguins data set from palmerpenguins package, find the mean and standard deviation of flipper_length_mm by species.

library(tidyverse)
library(palmerpenguins)
penguins |> drop_na() |> 
  group_by(species) |> 
  summarise(mean = mean(flipper_length_mm),
            sd = sd(flipper_length_mm))

Problem 5

Using the vector random_dates generated from the code below:

# Set the start and end dates
start_date <- as.POSIXct("2022-01-01 00:00:00")
end_date <- as.POSIXct("2022-12-31 23:59:59")

# Generate a vector of random dates and times between the start and end dates
random_dates <- as.POSIXct(runif(10, start_date, end_date), origin = "1970-01-01")

# Print the vector of random dates and times
random_dates

Use sapply() to determine what day of the week (in words) does the date represent. Hint: Look at the wday function from lubridate.

library(tidyverse)
sapply(random_dates, wday, label = TRUE)