Description Usage Arguments Details Value Connectivity Morphology See Also Examples

the `ngraph`

class contains a (completely general) graph
representation of a neuron's connectivity in an `igraph`

object. It
may additionally contain vertex name or position data. See Connectivity
section.

`ngraph()`

creates an ngraph from edge and vertex information.

`as.ngraph`

converts an object to an ngraph

`as.ngraph.dataframe`

construct ngraph from a data.frame
containing SWC format data

`as.ngraph.neuron`

construct ngraph from a neuron

1 2 3 4 5 6 7 8 9 10 11 | ```
ngraph(el, vertexnames, xyz = NULL, diam = NULL, directed = TRUE,
weights = FALSE, vertex.attributes = NULL, graph.attributes = NULL)
as.ngraph(x, ...)
## S3 method for class 'data.frame'
as.ngraph(x, directed = TRUE, ...)
## S3 method for class 'neuron'
as.ngraph(x, directed = TRUE, method = c("swc", "seglist"),
...)
``` |

`el` |
A two columm matrix (start, end) defining edges. |

`vertexnames` |
Integer names for graph nodes - the edge list is specified using these names (see details). |

`xyz` |
3D coordinates of vertices (optional, Nx3 matrix, or Nx4 matrix when 4th column is assumed to be diameter) |

`diam` |
Diameter of neuron at each vertex (optional) |

`directed` |
Whether the resultant graph should be directed (default TRUE) |

`weights` |
Logical value indicating whether edge weights defined by the
3D distance between points should be added to graph (default |

`vertex.attributes, graph.attributes` |
List of named attributes to be
added to the graph. The elements of |

`x` |
Object to convert (see method descriptions) |

`...` |
Arguments passed to methods |

`method` |
Whether to use the swc data (x$d) or the seglist to define neuronal connectivity to generate graph. |

Note that the `as.ngraph.neuron`

method *always* keeps the
original vertex names (a.k.a. PointNo) as read in from the original file.

an `igraph`

object with additional class `ngraph`

, having a
vertex for each entry in vertexnames, each vertex having a `label`

attribute. All vertices are included whether connected or not.

We make the following assumptions about neurons coming in

They have an integer vertex name that need not start from 1 and that may have gaps. This is analagous to the PointNo field of the core data block of

`neuron`

objects.The edge list that defines connectivity specifies those edges using pairs of vertex names, _not_ raw vertex indices.

We make no attempt to determine the root points at this stage.

The raw vertex ids in the graph will be in the order of vertexnames and can
therefore be used to index a block of vertex coordinates. The vertexnames
will be stored using the vertex attribute `name`

. The underlying
igraph class allows nodes to be specified by their name. This provides a
convenient way to define nodes in an ngraph object by the numeric
identifier encoded by the PointNo field of the corresponding
`neuron`

.

When the graph is directed (default) the edges will be from the root to the other tips of the neuron.

The morphology of the neuron is encoded by the combination of connectivity information (i.e. the graph) and spatial data encoded as the 3D position and diameter of each vertex. Position information is stored as vertex attributes X, Y, and Z.

`igraph`

, `set.vertex.attribute`

,
`subset.neuron`

for example of graph-based manipulation of a
neuron.

Other neuron: `neuron`

,
`plot.dotprops`

,
`potential_synapses`

, `prune`

,
`resample`

, `rootpoints`

,
`spine`

, `subset.neuron`

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | ```
n=Cell07PNs[[1]]
g=as.ngraph(n)
library(igraph)
# check that vertex attributes of graph match X position
all.equal(V(g)$X, n$d$X)
# Use 3D segment lengths as edge length of graph
gw=as.ngraph(n, weights=TRUE)
# find longest path across graph
d=get.diameter(gw)
# make a new neuron using the longest path
gw_spine=as.neuron(induced.subgraph(gw, d))
# make a new neuron containing all nodes except those in longest path
gw_antispine=as.neuron(delete.vertices(gw, d))
# note use of bounding box of original neuron to set plot axes
plot(gw_spine, col='red', boundingbox=boundingbox(n))
plot(gw_antispine, col='blue', add=TRUE)
``` |

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