SYNOPSIS
g_covar -f traj.xtc -s topol.tpr -n index.ndx -o eigenval.xvg -v eigenvec.trr -av average.pdb -l covar.log -ascii covar.dat -xpm covar.xpm -xpma covara.xpm -[no]h -[no]version -nice int -b time -e time -dt time -tu enum -xvg enum -[no]fit -[no]ref -[no]mwa -last int -[no]pbcDESCRIPTION
g_covar calculates and diagonalizes the (mass-weighted) covariance matrix. All structures are fitted to the structure in the structure file. When this is not a run input file periodicity will not be taken into account. When the fit and analysis groups are identical and the analysis is non mass-weighted, the fit will also be non mass-weighted.
The eigenvectors are written to a trajectory file ( -v). When the same atoms are used for the fit and the covariance analysis, the reference structure for the fit is written first with t=-1. The average (or reference when -ref is used) structure is written with t=0, the eigenvectors are written as frames with the eigenvector number as timestamp.
The eigenvectors can be analyzed with g_anaeig.
Option -ascii writes the whole covariance matrix to an ASCII file. The order of the elements is: x1x1, x1y1, x1z1, x1x2, ...
Option -xpm writes the whole covariance matrix to an .xpm file.
Option -xpma writes the atomic covariance matrix to an .xpm file, i.e. for each atom pair the sum of the xx, yy and zz covariances is written.
Note that the diagonalization of a matrix requires memory and time that will increase at least as fast as than the square of the number of atoms involved. It is easy to run out of memory, in which case this tool will probably exit with a 'Segmentation fault'. You should consider carefully whether a reduced set of atoms will meet your needs for lower costs.
FILES
-f traj.xtc InputTrajectory: xtc trr trj gro g96 pdb cpt
-s topol.tpr
Input
Structure+mass(db): tpr tpb tpa gro g96 pdb
-n index.ndx
Input, Opt.
Index file
-o eigenval.xvg
Output
xvgr/xmgr file
-v eigenvec.trr
Output
Full precision trajectory: trr trj cpt
-av average.pdb
Output
Structure file: gro g96 pdb etc.
-l covar.log
Output
Log file
-ascii covar.dat
Output, Opt.
Generic data file
-xpm covar.xpm
Output, Opt.
X PixMap compatible matrix file
-xpma covara.xpm
Output, Opt.
X PixMap compatible matrix file
OTHER OPTIONS
-[no]hnoPrint help info and quit
-[no]versionno
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)
-tu enum ps
Time unit: fs, ps, ns, us, ms or s
-xvg enum xmgrace
xvg plot formatting: xmgrace, xmgr or none
-[no]fityes
Fit to a reference structure
-[no]refno
Use the deviation from the conformation in the structure file instead of from the average
-[no]mwano
Mass-weighted covariance analysis
-last int -1
Last eigenvector to write away (-1 is till the last)
-[no]pbcyes
Apply corrections for periodic boundary conditions