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.

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Demo

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

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System Requirements

Ensure the following system dependencies are available:

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

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Getting Started

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

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_rex.yaml up --build

Local (not recommended)

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).

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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.

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Authentication

Rex supports:

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

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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.

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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

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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

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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.

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