cnapath {bio3d} | R Documentation

## Suboptimal Path Analysis for Correlation Networks

### Description

Find k shortest paths between a pair of nodes, source and sink, in a correlation network.

### Usage

    cnapath(cna, from, to=NULL, k=10, collapse=TRUE, ncore=NULL, ...)
    ## S3 method for class 'cnapath'
    summary(object, ..., pdb = NULL, label = NULL, col = NULL,
       plot = FALSE, concise = FALSE, cutoff = 0.1, normalize = TRUE, weight = FALSE)
    ## S3 method for class 'cnapath'
    print(x, ...)

### Arguments

`cna` | A ‘cna’ object obtained from `cna`.
`from` | Integer vector or matrix indicating node id(s) of source. If is matrix and `to` is NULL, the first column represents source and the second sink.
`to` | Integer vector indicating node id(s) of sink. All combinations of `from` and `to` values will be used as source/sink pairs.
`k` | Integer, number of suboptimal paths to identify.
`collapse` | Logical, if TRUE results from all source/sink pairs are merged with a single ‘cnapath’ object returned.
`ncore` | Number of CPU cores used to do the calculation. By default (NULL), use all detected CPU cores.
`object` | A ‘cnapath’ class of object obtained from `cnapath`. Multiple ‘object’ input is allowed for comparing paths from different networks.
`pdb` | A ‘pdb’ class of object obtained from `read.pdb` and is used as the reference for node residue ids (in `summary.cnapath`) or for molecular visulaization with VMD (in `vmd.cnapath`).
`label` | Character, label for paths identified from different networks.
`col` | Colors for plotting statistical results for paths identified from different networks.
`plot` | Logical, if TRUE path length distribution and node degeneracy will be plotted.
`concise` | Logical, if TRUE only ‘on path’ residues will be displayed in the node degeneracy plot.
`cutoff` | Numeric, nodes with node degeneracy larger than `cutoff` are shown in the output.
`normalize` | Logical, if TRUE node degeneracy is divided by the total (weighted) number of paths.
`weight` | Logical, if TRUE each path is weighted by path length in calculating the node degeneracty.
`x` | A 'cnapath' class object as obtained from function `cna`.
`...` | Additional arguments passed to igraph function `get.shortest.paths` (in the function `cnapath`), passed to `summary.cnapath` (in `print.cnapath`), as additional paths for comparison (in `summary.cnapath`).

### Value

The function `cnapath` returns a ‘cnapath’ class of list containing following three components:

`path` | a list object containing all identified suboptimal paths. Each entry of the list is a sequence of node ids for the path.
`epath` | a list object containing all identified suboptimal paths. Each entry of the list is a sequence of edge ids for the path.
`dist` | a numeric vector of all path lengths.

The function `summary.cnapath` returns a matrix of (normalized) node degeneracy for ‘on path’ residues.

### Author(s)

Xin-Qiu Yao

### References

Yen, J.Y. (1971) Management Science 17, 712–716.

### See Also

`cna`, `cna.dccm`, `vmd.cna`, `vmd.cnapath`, `get.shortest.paths`.

### Examples

    # Redundant testing excluded

    if (!requireNamespace("igraph", quietly = TRUE)) {
       message('Need igraph installed to run this example')
    } else {

    attach(transducin)
    inds = match(c("1TND_A", "1TAG_A"), pdbs$id)

    npdbs <- trim(pdbs, row.inds=inds)
    gaps.res <- gap.inspect(npdbs$ali)

    modes <- nma(npdbs)
    cij <- dccm(modes)
    net <- cna(cij, cutoff.cij=0.3)

    # get paths
    pa1 <- cnapath(net[[1]], from = 314, to=172, k=50)
    pa2 <- cnapath(net[[2]], from = 314, to=172, k=50)

    # print the information of a path
    pa1

    # print two paths simultaneously
    pas <- list(pa1, pa2)
    names(pas) <- c("GTP", "GDP")
    print.cnapath(pas)

    # Or, for the same effect,
    # summary(pa1, pa2, label=c("GTP", "GDP"))

    # replace node numbers with residue name and residue number in the PDB file
    pdb <- read.pdb("1tnd")
    pdb <- trim.pdb(pdb, atom.select(pdb, chain="A", resno=npdbs$resno[1, gaps.res$f.inds]))
    print.cnapath(pas, pdb=pdb)

    # plot path length distribution and node degeneracy
    print.cnapath(pas, pdb = pdb, col=c("red", "darkgreen"), plot=TRUE)

    # View paths in 3D molecular graphic with VMD
    #vmd.cnapath(pa1, pdb, launch = TRUE)
    #vmd.cnapath(pa1, pdb, colors = 7, launch = TRUE)
    #vmd.cnapath(pa1, pdb, spline=TRUE, colors=c("pink", "red"), launch = TRUE)
    #pdb2 <- read.pdb("1tag")
    #pdb2 <- trim.pdb(pdb2, atom.select(pdb2, chain="A", resno=npdbs$resno[2, gaps.res$f.inds]))
    #vmd.cnapath(pa2, pdb2, launch = TRUE)

    detach(transducin)

    }

[Package bio3d version 2.3-4 Index]