Rex: Shiny R/exams Dashboard

Rex is an easy-to-use Shiny dashboard for creating, managing, and evaluating written paper exams using R/exams. It is designed to simplify workflows for educators while supporting complex, randomized exercise formats and fully automated evaluation.

---

Demo

Access to a hosted demo version is free and available on request via email for testing and evaluation purposes.

---

Running Rex yourself

The following instructions assume a Linux environment. For Windows and macOS users, the setup is largely the same, but some steps, particularly regarding the rex.sqlite database file location and Docker Compose startup, may need minor adjustments based on your OS.

Docker (recommended)

Initial Setup

Download the database file rex.sqlite to your /home/ directory using curl or wget (you may need sudo to write to /home):

# Using curl
curl -L -o /home/rex.sqlite https://raw.githubusercontent.com/guesswho1234/Rex/main/rex.sqlite

# Using wget
wget -O /home/rex.sqlite https://raw.githubusercontent.com/guesswho1234/Rex/main/rex.sqlite

Alternatively, you can manually download and place it in your /home/ directory.

Set File Ownership and Permissions

Ensure the database file is owned by UID 1001 and GID 1001:

sudo chown 1001:1001 /home/rex.sqlite
sudo chmod 660 /home/rex.sqlite

Build and Run the Application

docker-compose -f compose.yaml up --build

Local (not recommended)

Ensure the following system dependencies are available:

• libsodium-dev
• libmagick++-dev
• libpoppler-cpp-dev
• ghostscript
• texlive-full
• pandoc

Install required R packages as listed in app.R and worker.R.

Then launch the app via:

shiny::runApp(appDir = '<base directory containing app.R>', host = '0.0.0.0', port = 3838)

⚠️ Depending on your OS and availability of dependencies, the app might be bugged or not run at all. In that case use docker instead (see previous section).

---

Security

Rex uses a hardened Docker setup:

• Non-root users with dropped capabilities
• Background worker has no network access
• Resource-limited containers

⚠️ Always audit third-party dependencies before deployment. Use at your own risk and follow security best practices.

---

Authentication

Rex supports:

• Basic login (default user: rex, password: rex)
• Single Sign-On (SSO) integration for OAuth 2.0 (configurable for institutional environments)

---

Usage

Browser recommendation: Firefox

Manage Exercises

Use the “EXERCISES” tab to manage exercises.

Rex supports two types of exercises:

1. Simple Exercises

These are created directly within the app using the UI. Ideal for users without programming experience.

• Fully editable in the app
• Supports inline math and full LaTeX environments
• Fields include:
  • Name, Author, Type, Points, Section
  • Question text and solution note
  • Answer options with true/false flags and notes
  • One PNG figure per exercise
  • Toggle LaTeX environments
• Can be exported to .RMD or .RNW format and later re-imported without losing editability

2. Advanced (Coded) Exercises

These are authored externally in .RMD or .RNW files using R features such as:

• Dynamic code chunks (e.g. random number generation)
• Custom LaTeX environments
• Arbitrary R logic for exercise generation

These exercises can be imported into Rex, but cannot be edited directly in the UI.

⚠️ You may optionally convert advanced exercises to simple ones for editing, but this can lead to loss of functionality or formatting.

---

Create Exams

Go to “EXAM” > “Create exam” to generate an exam.

Steps:

1. Ensure exercises are marked as examinable.
2. Configure options and click “Create exam”.
3. Download the generated ZIP archive, which includes:
   • PDF files of all exam versions — intended for printing and distribution to students
   • HTML files matching the PDF versions — include solutions and are meant for quality control before the exam
   • RDS file for later evaluation
   • All exercises used in the exam
   • input.txt — contains all parameter values used for exam creation
   • code.txt — R code to reproduce the exam outside of Rex

---

Evaluate Exams

Navigate to “EXAM” > “Evaluate exam”.

Required files:

• Solutions: RDS file from exam creation
• Participants: CSV (optional; dummy users will be used if omitted)
• Scans: PDF or PNG of evaluation sheets (same orientation recommended)

After evaluation:

• Manual review/editing of scans is possible
• Output ZIP includes:
  • Converted scans (*_nops_scan.zip)
  • Individual evaluation reports (*_nops_eval.zip)
  • Overall evaluation CSV
  • PDF report and raw statistics
  • input.txt and code.txt

---

Addons

Extend Rex with custom features like:

• Default values
• Additional UI fields
• Entirely new logic modules

⚠️ Addons may increase attack surface. Use at your own risk.

Commercial hosting

Dedicated deployment options and managed instances may be possible on request and can be discussed via email.

---