Import Linear Habitat Mask

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Description

Construct a linearmask from line data in a text file, a polyline shapefile, a dataframe or a SpatialLinesDataFrame object.

Usage

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read.linearmask(file = NULL, data = NULL, spacing = 10, spacingfactor =
1.5, graph = TRUE, cleanskips = TRUE,  ...)

Arguments

file

file name

data

data frame or SpatialLinesDataFrame

spacing

length of each discretized segment

spacingfactor

numeric criterion for joining mask points

graph

logical; if TRUE the igraph representation of the mask is saved as an attribute

cleanskips

logical; if TRUE then cleanskips is applied to the graph

...

other arguments passed to read.table for file input

Details

Only one of ‘file’ or ‘data’ should be specified. The file name should include the extension (e.g., "silverstream.shp").

Input from a text file, polyline shapefile or dataframe is first converted to a SpatialLinesDataFrame object. Points are spaced equally along each SpatialLine, starting at spacing / 2.

For dataframe input via data the coordinates are expected to be in columns ‘x’ and ‘y’; if these names are missing, or input is from a file, the first two columns are used.

spacingfactor is used by asgraph to determine which points are joined when computing distances. It should be between 1 and 2.

Value

A ‘linearmask’ object, i.e. a ‘mask’ object in which each point represents a line segment of length spacing, and with additional attributes ‘SLDF’, ‘spacingfactor’ and possibly ‘graph’ (see linearmask).

Note

A valid shapefile includes at least three files with extensions ‘.shp’, ‘.dbf’ and ‘.shx’. The full name of the .shp file is provided as the ‘file’ argument of read.linearmask. The shapefile name without any extension is used as the first argument to the maptools function readShapeSpatial.

Line-level covariates are copied from SpatialLinesDataFrame input. Point-specific covariates may be added later using covariates or addCovariates.

See Also

asgraph, linearmask, make.sldf, networkdistance, SpatialLinesDataFrame

Examples

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x <- seq(0, 4*pi, length = 200)
xy <- data.frame(x = x*100, y = sin(x)*300)
test <- read.linearmask(data = xy, spacing = 20)
plot(test)

xy2 <- data.frame(x = x*100, y = cos(x)*300)
test2 <- read.linearmask(data = xy2, spacing = 20)

plot(test2, add = TRUE)