[gmx-users] g_gyrate output columns meaning

[Dawid das]

Dear Gromacs experts,

How can I understand the relation between those four last columns:
@ s0 legend "Rg"
@ s1 legend "RgX"
@ s2 legend "RgY"
@ s3 legend "RgZ"
         0      1.6378      1.2375     1.37115     1.39762
         2      1.6433     1.25186     1.37786     1.39111
         4     1.64588     1.25053     1.37212     1.40403
         6     1.63929     1.25421       1.364     1.39319
         8     1.64384     1.25509     1.36634     1.40081

RgX, RgY and RgZ are values of radius of gyration about X, Y and Z axes,
respectively. And what is Rg? Is it like a total or resultant radius of
gyration? I read this explanation:
http://manual.gromacs.org/current/programs/gmx-gyrate.html but I'm still
not sure how to understand it.

Thank you,

Dawid