splitsegments: Split Segments by Endpoint Proximity

Description

Detects cases in which segments should be split to establish appropriate topology, and splits them. Specifically, it looks for segment endpoints intersecting (or within a tolerance of) another segment. It then splits the intersected segment at the point where the endpoint of the other segment breaks it.

Usage

splitsegments(
  rivers,
  tolerance = NULL,
  splitthese = NULL,
  splitthemat = NULL,
  one2one = FALSE,
  append = FALSE
)

Value

A new, updated river network object

Arguments

rivers: The river network object to use
tolerance: The spatial snapping tolerance to use for detecting intersection. If a NULL value is used (default), it will default to the tolerance that was used in river network creation in line2network.
splitthese: An optional vector of target segments to split. If this argument is used, only these segments will be split. If the default (NULL) is accepted, all segments will be used.
splitthemat: An optional vector of segments (endpoints) to use for splitting. If this argument is used, segments will only be split at the endpoints of these segments. If the default (NULL) is accepted, all segments will be used.
one2one: Logical, indicating a one-to-one correspondence between arguments splitthese and splitthemat. Defaults to FALSE,
append: Logical, indicating how to organize the output river network. If TRUE, appends newly-created segments to the end of $lines, rather than retaining original line ordering. This may be useful in retaining original line ID. Defaults to FALSE.

Author

Matt Tyers

Examples

Run this code

data(Koyukuk1)
topologydots(rivers=Koyukuk1)
# Segments 7, 8, 13, and 16 need to be split so topologies will work.  
# Since endpoints are not in the same place, they are not detected as 
# being connected.
plot(x=Koyukuk1)

Koyukuk1split <- splitsegments(rivers=Koyukuk1)
topologydots(rivers=Koyukuk1split)
plot(x=Koyukuk1split)

# if only segment 17 were to be split in three places
plot(x=splitsegments(rivers=Koyukuk1, splitthese=c(7,7,7),
        splitthemat=c(14,5,12)))
        
# if only segment 16 were to be split, showing behavior of append=
plot(x=splitsegments(rivers=Koyukuk1, splitthese=c(7,7,7),
        splitthemat=c(14,5,12), append=TRUE))