afni_proc.py does not honor the default setting of -volreg_warp_dxyz

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1

Hello,
I noticed that the output resolution of the EPI file by afni_proc.py does not reflect what the documentation says.
The documentation says this for the parameter -volereg_warp_dxyz.
-volreg_warp_dxyz DXYZ : grid dimensions for _align_e2a or _tlrc_warp

            e.g. -volreg_warp_dxyz 3.5
            default: min dim truncated to 3 significant bits

And it listed a few examples. My interpretation is that if I leave this parameter unset, then it should take the default above.
But for my dataset which has 2.694 mm on two dimensions and 2.7 mm on the other dimension, the output EPI file after volreg is 2.5 mm resolution, instead of 2.69 or 2.7 which I would guess based on the documentation.

Just wonder if you want to check whether the documentation is outdated or if the script somehow does not follow the default. (I am using AFNI version linux_openmp_64 19.2.07 from July 30.)

Thanks!

2

Hello,

Yes, it is applying the default: min dim truncated to 3 significant bits

Your min dimension seems to be 2.694. Truncating that to 3 significant bits yields 2.5.

Perhaps you are thinking “3 significant digits”, but it uses “bits”, not “digits”.

Please see the option help for examples.

  • rick
3

Thanks Rick. Now I see it!