Which columns represent which motion parameters in the file "dfile_rall.1D"

AFNI Message Board
1

The file “dfile_rall.1D” is located inside the folder of preprocessed time-series from AFNI proc. This file has 6 columns of datapoints. Each column represents one of the 6 motion parameters:

Three for translation:

  • y-axis
  • x-axis
  • z-axis

Three for rotation:

  • pitch
  • yaw
  • roll

My question is which column (1 to 6) corresponds to which translation and rotation parameters?
Thank you,
Philipp

2

Hi, Philipp-

That text file is output by 3dvolreg. 3dvolreg’s help describes the columns:


  -1Dfile ename   Save the motion parameters ONLY in file 'ename'.
                    The output is in 6 ASCII formatted columns:

                    roll pitch yaw dS  dL  dP

                  This file can be used in FIM as an 'ort', to detrend
                  the data against correlation with the movements.
                  This type of analysis can be useful in removing
                  errors made in the interpolation.

… where those rotations and translations are described previously in that same help file:


...
                    roll  = rotation about the I-S axis }
                    pitch = rotation about the R-L axis } degrees CCW
                    yaw   = rotation about the A-P axis }
                      dS  = displacement in the Superior direction  }
                      dL  = displacement in the Left direction      } mm
                      dP  = displacement in the Posterior direction }
...
       ** roll  = shaking head 'no' left-right
       ** pitch = nodding head 'yes' up-down
       ** yaw   = wobbling head sideways (ear toward shoulder)

Also consider displaying that file with either:


1dplot -volreg FILE
1dplot -sepscl -volreg FILE

… to see a labelled plot of the values.

–pt

3

Hi Paul,

thanks a lot, perfect.
Philipp

4

Hi,

just to confirm again:


-1Dfile ename   Save the motion parameters ONLY in file 'ename'.
                    The output is in 6 ASCII formatted columns:

                    roll pitch yaw dS  dL  dP

Hence, column 1 starts with roll and column 6 ends with dP. Correct?
I am asking this again because if I use the following code:


Results 1dplot -volreg dfile_rall.1D
1dplot -sepscl -volreg dfile_rall.1D

It plots:
A-P in the first row;
R-L in the second row;
I-S in the third row;
Yaw in the fourth row;
Pitch in the fith row;
Roll in the sixth row

The plotting order (from row one to the last row) does not match the column order (left to right) described above.

Two questions.

  1. Does the plotting order (top to bottom row) simply not follow the column order (left to right)?

Does “dS” correspond to the y-axis translation?
Does “dL” correspond to the x-axis translation?
Does “dP” correspond to the z-axis translation?

Thanks,
Philipp

5

Hi Philipp,

Actually, 1dplot plots from the bottom up.

  • rick
6

To answer your questions…

  1. Yes, 1dplot uses a bottom to top ordering.

  2. No, in dS, the S stands for Superior, and similarly for dL and dP standing for Left and Posterior. Those are independent of the ordering of the axes on disk.

  • rick
7

Thanks Rick, understood.

Philipp