A ‘skip’ is defined here as a graph edge between two input lines. Many skips are
legitimate, but some ‘shortcut’ skips are artefacts of the simple algorithm
used by `asgraph`

to construct the graph topology. These are
better removed. These functions allow skips in a linearmask to be visualised and edited.

`addedges`

may be used to bridge artefactual gaps in a network, or
to correct editing mistakes. The edge weight of a new edge is its Euclidean length.

1 2 3 4 5 6 7 8 9 10 |

`mask` |
linearmask object with 'graph' attribute |

`lengths` |
numeric vector of minimum and maximum edge length (weight) |

`plt` |
logical; if TRUE the edges are plotted |

`add` |
logical; if TRUE the edges will be added to an existing plot |

`type` |
character value for subset of edges to show |

`xlim` |
vector of min and max x-values for new plot |

`ylim` |
vector of min and max y-values for new plot |

`replot` |
logical; if TRUE the plot will be re-done using replot |

`...` |
other arguments (see details) |

`showedges`

is a general-purpose function for displaying or
extracting edge information from the graph attribute of a linear mask.

`cleanskips`

removes any between-line ‘skips’ that are longer
than the shortest ‘skip’.

Other functions here are used to manually edit a mask graph.

`replot`

is used to zoom in on part of a linear mask (often to inspect ‘skips’).

The dots argument ... is passed by `replot`

to `plot.linearmask`

and by `addedges`

and `deleteedges`

to `showedges`

(if replot = TRUE).

`showedges`

returns a dataframe with one row for each edge, and columns –

`start` |
index of start vertex |

`finish` |
index of finish vertex |

`line1` |
line number of start |

`line2` |
line number of finish |

`x1` |
geographic coordinates of start |

`y1` |
geographic coordinates of start |

`x2` |
geographic coordinates of finish |

`y2` |
geographic coordinates of finish |

`weight` |
"weight" attribute of edge (its length in metres) |

The dataframe is returned invisibly if `plt = TRUE`

.

`cleanskips`

returns a linearmask object.

`replot`

returns NULL.

`addedges`

and `deleteedges`

invisibly returns a linear mask
object with updated graph attribute.

linearmask, `getLineID`

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | ```
## Not run:
setwd(system.file("extdata", package = "secrlinear"))
tempmask <- read.linearmask(file = "silverstream.shp", spacing = 50)
## show all edges
plot(tempmask, linecol = 'white')
tmp <- showedges(tempmask, add = TRUE)
## select a rectangular area to zoom in
replot(tempmask)
## click on the vertices of one or more edges to delete or add
tempmask <- deleteedges(tempmask)
tempmask <- addedges(tempmask)
## End(Not run)
``` |

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