11  Debugging & Logging

When an analysis fails or produces unexpected output, JASP’s logging system helps you trace the problem.

11.1 Enabling Logging

  1. Open JASP.
  2. Click the hamburger menu (☰) → Preferences.
  3. Go to Advanced Preferences.
  4. Toggle logging on.

JASP writes one log per session, with separate files for the Desktop process and each Engine process.

11.2 Log File Locations

Platform Path
Windows %USERPROFILE%\AppData\Roaming\JASP\JASP\Logs
macOS ~/Library/Application Support/JASP/JASP/Logs/
Linux (Flatpak) ~/.var/app/org.jaspstats.JASP/data/JASP/JASP/Logs

11.2.1 Finding the Right Log

Logs are named: JASP YYYY-MM-DD HH_MM_SS Desktop.log (and Engine0.log, Engine1.log, etc.)

Collect all files with the same timestamp to get the complete picture for a single session.

11.3 Viewing Logs

11.3.1 From Within JASP

In Advanced Preferences, click Show Logs to open the log directory.

11.3.2 Command Line

Launch JASP from a terminal with --logToFile to also print output to the console:

/Applications/JASP.app/Contents/MacOS/JASP --logToFile
flatpak run org.jaspstats.JASP --logToFile
"C:\Program Files\JASP\JASP.exe" --logToFile 2>&1 | more

On Windows, pipe the output to more or redirect to a file to see it, since the console does not display output by default.

11.4 When JASP Won’t Start

If JASP crashes on startup, logs are often still written before the crash. Use the command-line launch method above to capture output, or check the log directory manually for the most recent files.

11.5 Debugging R Code

For R analysis issues, it is often faster to debug outside JASP using jaspTools and R’s browser() function. See Chapter 7 for the full workflow, including:

  • Running analyses interactively with jaspTools::runAnalysis()
  • Setting breakpoints with browser()
  • Inspecting jaspResults objects mid-execution
  • The renv bootstrap script for setting up your environment
  1. Use RStudio’s debugger (browser(), breakpoints) as usual.

11.6 Common Issues

Symptom Likely cause Fix
Analysis shows red error R code threw an error Check Engine log for stack trace; debug in RStudio
Analysis runs but table is empty Table not filled or wrong $dependOn key Check that addRows() / setData() is called and dependencies match QML option names
Plot is blank ggplot object not assigned to plot element Verify plotObj$plotObject <- ggplot(...)
Module won’t load DESCRIPTION or NAMESPACE error Check that R CMD INSTALL . succeeds without warnings
Options not reaching R QML name doesn’t match R options[[...]] key Compare QML name: values with R option access