[gmx-users] Meaning of columns in .xvg output file

[Kamps, M.]

Dear gmx-users,

I've got a small question of which I can't find the answer. I have a
simulation where I want to calculate the average velocity of certain
particles. I've created an output .xvg file via the command:
gmx traj -f input.trr -s input.tpr -n input.ndx -av output.xvg
My output, is as requested an .xvg file which can be plotted in xmgrace.

However, when opening this .xvg file with a text-editor, it has four
columns of output, of which only the first two columns will be used by
xmgrace. The first column is a simple counter, however the other three
columns all contain values. Supposedly, the second column (column 2 of
4) contains the average velocities. My question: What are the values
in column 3 and 4?

Mark