---
name: "g_sgangle"
section: "1"
platform: "linux"
package: "gromacs-data"
version: "4.5.5-2"
release: "Debian 7 (Wheezy)"
platforms: ["linux"]
url: "https://new.carta.tech/g_sgangle"
---

# g\_sgangle(1)

computes the angle and distance between two groups VERSION 4.5.4-dev-20110404-bc5695c

## NAME

g\_sgangle - computes the angle and distance between two groups

**VERSION 4.5.4-dev-20110404-bc5695c**

## SYNOPSIS

**g\_sgangle** **-f** *traj.xtc*  **-n** *index.ndx*  **-s** *topol.tpr*  **-oa** *sg\_angle.xvg*  **-od** *sg\_dist.xvg*  **-od1** *sg\_dist1.xvg*  **-od2** *sg\_dist2.xvg*  **-\[no\]h** **-\[no\]version** **-nice** *int*  **-b** *time*  **-e** *time*  **-dt** *time*  **-\[no\]w** **-xvg** *enum*  **-\[no\]one** **-\[no\]z**

## DESCRIPTION

Compute the angle and distance between two groups.  The groups are defined by a number of atoms given in an index file and may be two or three atoms in size. If  **-one** is set, only one group should be specified in the index file and the angle between this group at time 0 and t will be computed. The angles calculated depend on the order in which the atoms are  given. Giving, for instance, 5 6 will rotate the vector 5-6 with  180 degrees compared to giving 6 5.

If three atoms are given,  the normal on the plane spanned by those three atoms will be calculated, using the formula  P1P2 x P1P3. The cos of the angle is calculated, using the inproduct of the two normalized vectors.

Here is what some of the file options do:

 **-oa**: Angle between the two groups specified in the index file. If a group contains three atoms the normal to the plane defined by those three atoms will be used. If a group contains two atoms, the vector defined by those two atoms will be used.

 **-od**: Distance between two groups. Distance is taken from the center of one group to the center of the other group.

 **-od1**: If one plane and one vector is given, the distances for each of the atoms from the center of the plane is given separately.

 **-od2**: For two planes this option has no meaning.

## FILES

**-f** *traj.xtc* **Input**\
  Trajectory: xtc trr trj gro g96 pdb cpt

**-n** *index.ndx* **Input**\
  Index file

**-s** *topol.tpr* **Input**\
  Run input file: tpr tpb tpa

**-oa** *sg\_angle.xvg* **Output**\
  xvgr/xmgr file

**-od** *sg\_dist.xvg* **Output, Opt.**\
  xvgr/xmgr file

**-od1** *sg\_dist1.xvg* **Output, Opt.**\
  xvgr/xmgr file

**-od2** *sg\_dist2.xvg* **Output, Opt.**\
  xvgr/xmgr file

## OTHER OPTIONS

**-\[no\]h***no*    \
  Print help info and quit

**-\[no\]version***no*    \
  Print version info and quit

**-nice** *int* **19**\
  Set the nicelevel

**-b** *time* **0**     \
  First frame (ps) to read from trajectory

**-e** *time* **0**     \
  Last frame (ps) to read from trajectory

**-dt** *time* **0**     \
  Only use frame when t MOD dt = first time (ps)

**-\[no\]w***no*    \
  View output  **.xvg**,  **.xpm**,  **.eps** and  **.pdb** files

**-xvg** *enum* **xmgrace**\
  xvg plot formatting:  **xmgrace**,  **xmgr** or  **none**

**-\[no\]one***no*    \
  Only one group compute angle between vector at time zero and time t

**-\[no\]z***no*    \
  Use the  *z*-axis as reference

## SEE ALSO

**[gromacs(7)](/gromacs/7.md)**

More information about **GROMACS** is available at \<*http://www.gromacs.org/*\>.