Methods to subset linear mask objects.

1 2 |

`x` |
linearmask object from |

`subset` |
numeric or logical vector to select rows of mask |

`LineID` |
vector of identifiers for lines to retain |

`droplinesbeyond` |
logical; distance criterion for dropping lines (m) |

`...` |
other arguments (not used) |

Specify only one of ‘subset’ and ‘LineID’.

If the input object has a ‘graph’ attribute then a new graph will be included in the output.

`subset.linearmask`

leaves the underlying SpatialLinesDataFrame
intact unless either (i) `LineID`

is specified, or (ii) a finite value is provided for `droplinesbeyond`

. `droplinesbeyond`

retains lines that have at least one point within the specified distance of at least one mask point, after subsetting.

A linearmask object.

`read.linearmask`

, linearmask

1 2 3 4 5 6 7 8 9 10 11 12 13 14 | ```
## rbind two linear masks,
x <- seq(0, 4*pi, length = 200)
xy <- data.frame(x = x*100, y = sin(x)*300)
xy2 <- data.frame(x = x*100, y = cos(x)*300)
test <- read.linearmask(data = xy, spacing = 10)
test2 <- read.linearmask(data = xy2, spacing = 10)
test3 <- rbind(test, test2)
table(covariates(test3)$LineID)
## then retrieve one...
test4 <- subset(test3, LineID = '1.1')
## ... or the other
test5 <- subset(test3, LineID = '2.1')
``` |

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