We have identified a significant issue affecting 3dMVM whenever the R package phia (version 0.3.1) is installed. This version of phia produces incorrect degrees of freedom for t-statistics in the output, an issue that may not be obvious unless closely inspected.
A corrected version of the package (phia 0.3.2) was released in May 30 2025, and updating phia resolves the problem.
How to check your current phia version
Run the following at your terminal:
R -e "packageVersion('phia')"
If the output shows:
[1] ‘0.3.1’
you must update the package.
How to update phia
Use the following command at the terminal:
R -e "install.packages('phia', repos='https://cloud.r-project.org')"
If you previously ran 3dMVM with phia 0.3.1
You should rerun your analyses with the updated phia version to ensure accurate degrees of freedom for correct t-statistics results.
Moving forward
We have now updated 3dMVM on GitHub so that the next AFNI release will detect phia 0.3.1 and stop with a message prompting users to update.
Please spread the word to anyone who may be affected.
Gang Chen