Hi Rick,
I have a question regarding the values in motion_deriv.1D file (generated by afni_proc.py, or actually by 1d_tool.py with -derivative option). When I look at the enorm values (from motion_sub01_enorm.1D), it makes sense to me that the first value of each run is 0, since the derivatives of each run are specified to 0. However, in motion_deriv.1D, there are small numbers for the first volume (TR) of each run. And it seems that all derivatives for following TRs in that run are adjusted by these small numbers of the first TR, as compared to the situation of specifying derivatives for the first TR to 0. Where do these numbers come from? and why? e.g., for use in regression? Thanks!
Qiuhai
