In kate-pyper/MM916ProgrammingExercises:

library(learnr)
library(testwhat)
knitr::opts_chunk$set(echo = FALSE, message=FALSE)
tutorial_options(exercise.timelimit = 60, exercise.checker=testwhat::testwhat_learnr)

require(tidyverse)

penguins<- readr::read_csv("https://raw.githubusercontent.com/rfordatascience/tidytuesday/master/data/2020/2020-07-28/penguins.csv")

penguins<- readr::read_csv("https://raw.githubusercontent.com/rfordatascience/tidytuesday/master/data/2020/2020-07-28/penguins.csv")

These exercises will explore the penguins data set using histograms.

head(penguins)

Exercise 1

Produce a histogram of the bill depth.

ggplot(penguins) +
  geom_histogram(aes(bill_depth_mm))

ex() %>% {
  check_error(.)
  check_function(., "ggplot") %>% check_arg(., "data")
  check_function(., "geom_histogram") %>% check_arg(., "mapping") %>% check_equal(., incorrect_msg="Check the contents of aes(), have you selected the correct variable?")
}

Exercise 2

Produce a histogram of the flipper length - make the bars of the histogram blue:

ggplot(penguins) +
  geom_histogram(aes(flipper_length_mm), fill="blue")

ex() %>% {
  check_error(.)
  check_function(., "ggplot") %>% check_arg(., "data")
  check_function(., "geom_histogram") %>% {
    check_arg(., "mapping") %>% check_equal(., incorrect_msg="Check the contents of aes(), have you selected the correct variable?")
    check_arg(., "fill", arg_not_specified_msg = "Use fill to change the bar colours") 
  }
}

Exercise 3

The previous histogram has two "bumps" (the technical term for this is multimodal). Produce a histogram of flipper length by species:

ggplot(penguins) +
  # It is useful to specify alpha to be small to make the plot easier to read
  geom_histogram(aes(flipper_length_mm, fill=species), alpha=0.2)

ex() %>% {
  check_error(.)
  check_function(., "ggplot") %>% check_arg(., "data")
  check_function(., "geom_histogram") %>% check_arg(., "mapping") %>% check_equal(., incorrect_msg="Check the contents of aes(), have you selected the correct variable?")
}