Merge release-5-0 into master

[alexxy/gromacs.git] / docs / manual / analyse.tex

diff --git a/docs/manual/analyse.tex b/docs/manual/analyse.tex
index d235e9c45491fc27a73f753b3453b2cde4365b85..42038f5c395206aa376902e8f8324ab1a20a1dd4 100644 (file)
--- a/docs/manual/analyse.tex
+++ b/docs/manual/analyse.tex
@@ -724,7 +724,13 @@ R_g ~=~ \left({\frac{\sum_i \|{\bf r}_i\|^2 m_i}{\sum_i m_i}}\right)^{\half}
 \eeq
 where $m_i$ is the mass of atom $i$ and ${\bf r}_i$ the position of 
 atom $i$ with respect to the center of mass of the molecule. It is especially 
-useful to characterize polymer solutions and proteins.
+useful to characterize polymer solutions and proteins. The program will also
+provide the radius of gyration around the coordinate axis (or, optionally, principal axes)
+by only summing the radii components orthogonal to each axis, for instance
+\beq
+R_{g,x} ~=~ \left({\frac{\sum_i \left( r_{i,y}^2 + r_{i,z}^2 \right) m_i}{\sum_i m_i}}\right)^{\half}
+\label{eqn:rg}
+\eeq
 
 Sometimes it is interesting to plot the {\em distance} between two atoms,
 or the {\em minimum} distance between two groups of atoms