Summary and Setup

In this course we will look at how to extract data from databases using APIs in R.

We start with the GET method, to get bad dad jokes.

We continue using the POST method which allow more advanced searches. We apply it to the API provided by Statistics Denmark.

Finally the package danstat is introduced. This provides an easier way to interact with Statistics Denmark.

This is not an introduction to R

In this couse we assume you have the knowledge equivalent to attending one of our introductory courses

  • Have R and R-studio installed
    • Alternatively run everything on rstudio.cloud
  • Know how to assign values to variables
  • Know what a function is, and how we pass input and parameters to it
  • Be familiar with the %>% operator
  • Know the basic verbs from dplyr of the tidyverse:
    • select
    • filter
    • mutate
    • arrange
    • summarise
  • Be familiar with dataframes
  • Know how to install and load packages
  • Know how to comment your code
  • Know how to do math on variables
  • Get the concept of vectors
  • Subsetting vectors and dataframes
    • Using logical tests
  • Use NA to encode missing values
  • Read in data from a csv/excel

New concepts in R

Three concepts are typically not covered in our introductions.

  • factors
  • dates
  • lists

We will look at them when we need them.

Software Setup

Warning

Please do NOT install R and RStudio on Onedrive or other clouddrives. R will work but you will not be able to install the extensions to R that you will need in this course!

Installing R and RStudio

R and RStudio are separate downloads and installations. R is the underlying statistical computing environment, but using R alone is no fun. RStudio is a graphical integrated development environment (IDE) that makes using R much easier and more interactive. You need to install R before you install RStudio. Once installed, because RStudio is an IDE, RStudio will run R in the background. You do not need to run it separately.

Rather than installing R and RStudio on your personal computer, Posit Cloud offers a free, online alternative, where you will be able to run R and RStudio in your browser. Sign up with your Google/Gmail account if you have one, or with any other email.

The free version of RStudio Cloud places limitations on the number of projects you can work on, and the amount of memory and processing power you can access. For the purposes of following these lessons, RStudio Cloud is perfectly adequate, and what we recommend if you have any problems installing R and RStudio on your personal computer.

If you already have R and RStudio installed

  • Open RStudio, and click on “Help” > “Check for updates”. If a new version is available, quit RStudio, and download the latest version for RStudio.
  • To check which version of R you are using, start RStudio and the first thing that appears in the console indicates the version of R you are running. Alternatively, you can type sessionInfo(), which will also display which version of R you are running. Go on the CRAN website and check whether a more recent version is available. If so, please download and install it. You can check here for more information on how to remove old versions from your system if you wish to do so.

If you don’t have R and RStudio installed

  • Download R from the CRAN website.
  • Run the .exe file that was just downloaded.
  • Go to the RStudio download page.
  • Under Installers select RStudio x.yy.zzz - Windows. Vista/7/8/10 (where x, y, and z represent version numbers).
  • Double click the file to install it.
  • Once it’s installed, open RStudio to make sure it works and you don’t get any error messages.

If you already have R and RStudio installed

  • Open RStudio, and click on “Help” > “Check for updates”. If a new version is available, quit RStudio, and download the latest version for RStudio.
  • To check the version of R you are using, start RStudio and the first thing that appears on the terminal indicates the version of R you are running. Alternatively, you can type sessionInfo(), which will also display which version of R you are running. Go on the CRAN website and check whether a more recent version is available. If so, please download and install it. In any case, make sure you have at least R 3.2.

If you don’t have R and RStudio installed

  • Download R from the CRAN website.
  • Select the .pkg file for the latest R version.
  • Double click on the downloaded file to install R.
  • It is also a good idea to install XQuartz (needed by some packages).
  • Go to the RStudio download page.
  • Under Installers select RStudio x.yy.zzz - Mac OS X 10.6+ (64-bit) (where x, y, and z represent version numbers).
  • Double click the file to install RStudio.
  • Once it’s installed, open RStudio to make sure it works and you don’t get any error messages.
  • Follow the instructions for your distribution from CRAN, they provide information to get the most recent version of R for common distributions. For most distributions, you could use your package manager (e.g., for Debian/Ubuntu run sudo apt-get install r-base, and for Fedora sudo yum install R), but we don’t recommend this approach as the versions provided by this approach are usually out of date. In any case, make sure you have at least R 3.2.
  • Go to the RStudio download page.
  • Under Installers select the version that matches your distribution, and install it with your preferred method (e.g., with Debian/Ubuntu sudo dpkg -i rstudio-x.yy.zzz-amd64.deb at the terminal).
  • Once it’s installed, open RStudio to make sure it works and you don’t get any error messages.