g_cluster can cluster structures using several different methods. Distances between structures can be determined from a trajectory or read from an .xpm matrix file with the -dm option. RMS deviation after fitting or RMS deviation of atom-pair distances can be used to define the distance between structures.
single linkage: add a structure to a cluster when its distance to any element of the cluster is less than cutoff.
Jarvis Patrick: add a structure to a cluster when this structure and a structure in the cluster have each other as neighbors and they have a least P neighbors in common. The neighbors of a structure are the M closest structures or all structures within cutoff.
Monte Carlo: reorder the RMSD matrix using Monte Carlo.
diagonalization: diagonalize the RMSD matrix.
gromos: use algorithm as described in Daura
When the clustering algorithm assigns each structure to exactly one cluster (single linkage, Jarvis Patrick and gromos) and a trajectory file is supplied, the structure with the smallest average distance to the others or the average structure or all structures for each cluster will be written to a trajectory file. When writing all structures, separate numbered files are made for each cluster.
Two output files are always written:
-o writes the RMSD values in the upper left half of the matrix and a graphical depiction of the clusters in the lower right half When -minstruct = 1 the graphical depiction is black when two structures are in the same cluster. When -minstruct > 1 different colors will be used for each cluster.
-g writes information on the options used and a detailed list of all clusters and their members.
Additionally, a number of optional output files can be written:
-dist writes the RMSD distribution.
-ev writes the eigenvectors of the RMSD matrix diagonalization.
-sz writes the cluster sizes.
-tr writes a matrix of the number transitions between cluster pairs.
-ntr writes the total number of transitions to or from each cluster.
-clid writes the cluster number as a function of time.
-cl writes average (with option -av) or central structure of each cluster or writes numbered files with cluster members for a selected set of clusters (with option -wcl, depends on -nst and -rmsmin). The center of a cluster is the structure with the smallest average RMSD from all other structures of the cluster.
|-f||traj.xtc||Input, Opt.||Trajectory: xtc trr trj gro g96 pdb cpt|
|-s||topol.tpr||Input, Opt.||Structure+mass(db): tpr tpb tpa gro g96 pdb|
|-n||index.ndx||Input, Opt.||Index file|
|-dm||rmsd.xpm||Input, Opt.||X PixMap compatible matrix file|
|-o||rmsd-clust.xpm||Output||X PixMap compatible matrix file|
|-dist||rmsd-dist.xvg||Output, Opt.||xvgr/xmgr file|
|-ev||rmsd-eig.xvg||Output, Opt.||xvgr/xmgr file|
|-sz||clust-size.xvg||Output, Opt.||xvgr/xmgr file|
|-tr||clust-trans.xpm||Output, Opt.||X PixMap compatible matrix file|
|-ntr||clust-trans.xvg||Output, Opt.||xvgr/xmgr file|
|-clid||clust-id.xvg||Output, Opt.||xvgr/xmgr file|
|-cl||clusters.pdb||Output, Opt.||Trajectory: xtc trr trj gro g96 pdb cpt|
|-[no]h||bool||no||Print help info and quit|
|-[no]version||bool||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)|
|-tu||enum||ps||Time unit: fs, ps, ns, us, ms or s|
|-[no]w||bool||no||View output .xvg, .xpm, .eps and .pdb files|
|-xvg||enum||xmgrace||xvg plot formatting: xmgrace, xmgr or none|
|-[no]dista||bool||no||Use RMSD of distances instead of RMS deviation|
|-nlevels||int||40||Discretize RMSD matrix in this number of levels|
|-cutoff||real||0.1||RMSD cut-off (nm) for two structures to be neighbor|
|-[no]fit||bool||yes||Use least squares fitting before RMSD calculation|
|-max||real||-1||Maximum level in RMSD matrix|
|-skip||int||1||Only analyze every nr-th frame|
|-[no]av||bool||no||Write average iso middle structure for each cluster|
|-wcl||int||0||Write the structures for this number of clusters to numbered files|
|-nst||int||1||Only write all structures if more than this number of structures per cluster|
|-rmsmin||real||0||minimum rms difference with rest of cluster for writing structures|
|-method||enum||linkage||Method for cluster determination: linkage, jarvis-patrick, monte-carlo, diagonalization or gromos|
|-minstruct||int||1||Minimum number of structures in cluster for coloring in the .xpm file|
|-[no]binary||bool||no||Treat the RMSD matrix as consisting of 0 and 1, where the cut-off is given by -cutoff|
|-M||int||10||Number of nearest neighbors considered for Jarvis-Patrick algorithm, 0 is use cutoff|
|-P||int||3||Number of identical nearest neighbors required to form a cluster|
|-seed||int||1993||Random number seed for Monte Carlo clustering algorithm|
|-niter||int||10000||Number of iterations for MC|
|-kT||real||0.001||Boltzmann weighting factor for Monte Carlo optimization (zero turns off uphill steps)|