Connecting GitHub and Posit Cloud

You should have already received an invitation to join the GitHub organization for this course. You need to accept the invitation before moving on to the next step.

To connect your Posit and GitHub accounts by following the steps below:

• Click on your name on the top right corner to open the right menu.
• Then, click on Authentication.

• In the Authentication window, check the box for Enabled.

• In the next window, click on the green box that says “Authorize rstudio”.

• Back in the Authentication window, check the box for Private repo access also enabled, and once again, on the green box that says “Authorize rstudio” in the next window. At this point you should also make sure that the course organization shows up for you under Organization access. If it does not, this means you have not yet accepted the GitHub invitation to join the course, and you should go back and do that.

• Once you’re done, both of these boxes should be checked.

• To confirm that you’ve successfully linked up your GitHub and Posit Cloud accounts, GitHub settings > Applications. You should see Posit listed as an authorized app under Authorized OAuth Apps. If you don’t this is a good time to ask a question.

Getting started

Each of your assignments will begin with the following steps. You saw these once in class yesterday, they’re outlined in detail here again. Going forward each lab will start with a “Getting started” section but details will be a bit more sparse than this. You can always refer back to this lab for a detailed list of the steps involved for getting started with an assignment.

• Click on the assignment link that you should have received in your email to create your GitHub repository (which we’ll refer to as “repo” going forward) for the assignment. This repo contains a template you can build on to complete your assignment.

• On GitHub, click on the green Code button. The button used to be called “Clone or download”, select Use HTTPS (this might already be selected by default, and if it is, you’ll see the text Clone with HTTPS as in the image below). Click on the clipboard icon to copy the repo URL.

• Go to Posit Cloud and into the course workspace. Create a New Project from Git Repo. You will need to click on the down arrow next to the New Project button to see this option.

• Copy and paste the URL of your assignment repo into the dialog box:

• Hit OK, and you’re good to go!

install.packages("usethis") # Install the package
library(usethis) # Load the package
git_sitrep()

create_github_token()

Warm up

Before we introduce the data, let’s warm up with some simple exercises.

⊕The top portion of your R Markdown file (between the three dashed lines) is called YAML. It stands for “YAML Ain’t Markup Language”. It is a human friendly data serialization standard for all programming languages. All you need to know is that this area is called the YAML (we will refer to it as such) and that it contains meta information about your document.

YAML

Open the R Markdown (Rmd) file in your project, change the author name to your name, and knit the document.

Committing changes

Then go to the Git pane in your Posit.

If you have made changes to your Rmd file, you should see it listed here. Click on it to select it in this list and then click on Diff. This shows you the difference between the last committed state of the document and its current state that includes your changes. If you’re happy with these changes, write “Update author name” in the Commit message box and hit Commit.

You don’t have to commit after every change, this would get quite cumbersome. You should consider committing states that are meaningful to you for inspection, comparison, or restoration. In the first few assignments we will tell you exactly when to commit and in some cases, what commit message to use. As the semester progresses we will let you make these decisions.

Pushing changes

Now that you have made an update and committed this change, it’s time to push these changes to the web! Or more specifically, to your repo on GitHub. Why? So that others can see your changes. And by others, we mean the course teaching team (your repos in this course are private to you and us, only).

In order to push your changes to GitHub, click on Push. This will prompt a dialogue box where you first need to enter your user name, and then your password.

install.packages("tidyverse")
install.packages("datasauRus")

library(tidyverse) 
library(datasauRus)

Exercises

⊕The ✏️ symbol is a reminder to write a written response discussing the questions in the exercises.

1. ✏️ Based on the help file, how many rows and how many columns does the datasaurus_dozen file have? What are the variables included in the data frame? Add your responses to your lab report.

Let’s take a look at what these datasets are. To do so we can make a frequency table of the dataset variable:

datasaurus_dozen %>%
  count(dataset) %>%
  print(13)

## # A tibble:
## #   13 × 2
##   dataset 
##   <chr>   
## 1 away    
## 2 bullseye
## 3 circle  
## 4 dino    
## 5 dots    
## 6 h_lines 
## # ℹ 7 more
## #   rows
## # ℹ 1 more
## #   variable:
## #   n <int>

⊕Matejka, Justin, and George Fitzmaurice. “Same stats, different graphs: Generating datasets with varied appearance and identical statistics through simulated annealing.” Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems. ACM, 2017.

The original Datasaurus (dino) was created by Alberto Cairo in this great blog post. The other Dozen were generated using simulated annealing and the process is described in the paper Same Stats, Different Graphs: Generating Datasets with Varied Appearance and Identical Statistics through Simulated Annealing by Justin Matejka and George Fitzmaurice. In the paper, the authors simulate a variety of datasets that have the same summary statistics as the Datasaurus but have very different distributions.

🧶 ✅ ⬆️ Knit, commit, and push your changes to GitHub with the commit message “Add answer for Ex 1”. Make sure to commit and push all changed files so that your Git pane is cleared up afterwards.

2. Plot y vs. x for the dino dataset. Then, calculate the correlation coefficient between x and y for this dataset.

Below is the code you will need to complete this exercise. Basically, the answer is already given, but you need to include relevant bits in your Rmd document and successfully knit it and view the results.

Start with the datasaurus_dozen and pipe it into the filter function to filter for observations where dataset == "dino". Store the resulting filtered data frame as a new data frame called dino_data.

dino_data <- datasaurus_dozen %>%
  filter(dataset == "dino")

There is a lot going on here, so let’s slow down and unpack it a bit.

First, the pipe operator: %>%, takes what comes before it and sends it as the first argument to what comes after it. So here, we’re saying filter the datasaurus_dozen data frame for observations where dataset == "dino".

Second, the assignment operator: <-, assigns the name dino_data to the filtered data frame.

Next, we need to visualize these data. We will use the ggplot function for this. Its first argument is the data you’re visualizing. Next we define the aesthetic mappings. In other words, the columns of the data that get mapped to certain aesthetic features of the plot, e.g. the x axis will represent the variable called x and the y axis will represent the variable called y. Then, we add another layer to this plot where we define which geometric shapes we want to use to represent each observation in the data. In this case we want these to be points, hence geom_point.

ggplot(data = dino_data, mapping = aes(x = x, y = y)) +
  geom_point()

If this seems like a lot, it is. And you will learn about the philosophy of building data visualizations in layer in detail next week. For now, follow along with the code that is provided.

For the second part of these exercises, we need to calculate a summary statistic: the correlation coefficient. Correlation coefficient, often referred to as \(r\) in statistics, measures the linear association between two variables. You will see that some of the pairs of variables we plot do not have a linear relationship between them. This is exactly why we want to visualize first: visualize to assess the form of the relationship, and calculate \(r\) only if relevant. In this case, calculating a correlation coefficient really doesn’t make sense since the relationship between x and y is definitely not linear – it’s dinosaurial!

But, for illustrative purposes, let’s calculate the correlation coefficient between x and y.

⊕Start with dino_data and calculate a summary statistic that we will call r as the correlation between x and y.

dino_data %>%
  summarize(r = cor(x, y))

## # A tibble: 1 × 1
##         r
##     <dbl>
## 1 -0.0645

🧶 ✅ ⬆️ Knit, commit, and push your changes to GitHub with the commit message “Add answer for Ex 2”. Make sure to commit and push all changed files so that your Git pane is cleared up afterwards.

3. ✏️ Plot y vs. x for the star dataset. You can (and should) reuse code we introduced above, just replace the dataset name with the desired dataset. Then, calculate the correlation coefficient between x and y for this dataset. How does this value compare to the r of dino? Write a sentence based on your comparison.

🧶 ✅ ⬆️ This is another good place to pause, knit, commit changes with the commit message “Add answer for Ex 3”, and push. Make sure to commit and push all changed files so that your Git pane is cleared up afterwards.

4. ✏️ Plot y vs. x for the circle dataset. You can (and should) reuse code we introduced above, just replace the dataset name with the desired dataset. Then, calculate the correlation coefficient between x and y for this dataset. How does this value compare to the r of dino? Write a sentence based on your comparison.

🧶 ✅ ⬆️ You should pause again, commit changes with the commit message “Add answer for Ex 4”, and push. Make sure to commit and push all changed files so that your Git pane is cleared up afterwards.

⊕Facet by the dataset variable, placing the plots in a 3 column grid, and don’t add a legend.

5. Finally, let’s plot all datasets at once. In order to do this we will make use of faceting.

ggplot(datasaurus_dozen, aes(x = x, y = y, color = dataset))+
  geom_point()+
  facet_wrap(~ dataset, ncol = 3) +
  theme(legend.position = "none")

And we can use the group_by function to generate all the summary correlation coefficients.

datasaurus_dozen %>%
  group_by(dataset) %>%
  summarize(r = cor(x, y)) %>%
  print(13)

🧶 ✅ ⬆️ Yay, you’re done! Commit all remaining changes, use the commit message “Finish Lab 1! 💪“, and push. Make sure to commit and push all changed files so that your Git pane is cleared up afterwards. Before you wrap up the assignment, make sure all documents are updated on your GitHub repo. Use the self check list in the Readme to review.