pleistoshape_all: Calculate area, perimeter and surface area of islands over...

In g33k5p34k/PleistoDistR: Calculating Island Geomorphologies Over Pleistocene Time

Calculate area, perimeter and surface area of islands over time

Description

This function calculates the area, perimeter, and surface area of user-specified islands at each time/sea level interval, and performs the same calculations as the pleistoshape_area(), pleistoshape_perimeter, and pleistoshape_surfacearea() functions combined. This function is nonetheless provided since it allows users to calculate all three shape metrics simultaneously, which is faster than running each constituent function individually. PleistoDist will return a value of NA if the island is submerged underwater for that particular interval. After calculating shape metrics for each interval, this function calculates the time-weighted average area, perimeter, and surface area of each selected island.

Usage

pleistoshape_all(points, epsg, intervalfile, mapdir, outdir)

Arguments

points	A user-generated multi-point shapefile (.shp) containing at least two points. If the shapefile attribute table contains a column labelled 'Name', the output distance matrix will use the identifiers in this column to label each pairwise comparison. Otherwise, the output distance matrix will use the attribute FID values instead.
epsg	The projected coordinate system in EPSG code format. Because of the curvature of the Earth's surface, we need to apply a map projection to accurately calculate straight-line distances between points instead of using the default WGS84 geographical coordinate system. Users should specify a projected coordinate system appropriate to the geographic region being analysed using the projection's associated EPSG code (https://epsg.org/home). Geographic coordinate system projections are not recommended as those will result in distance matrices calculated in decimal degrees rather than in distance units.
intervalfile	This is the master control file generated using either the getintervals_time() or getintervals_sealvl() function that defines the number of intervals, the sea level at each interval, and the duration of each interval. By default, this function will use the "intervals.csv" file stored in the output folder, but users can also specify their own custom interval file (with nice round mean sea level values, for example), although users need to ensure that the same column names are preserved, and be aware that custom interval files may lead to inaccurate weighted mean calculations.
mapdir	The directory containing map outputs from the makemaps() function (i.e. the directory containing the raster_flat, raster_topo, and shapefile folders).
outdir	Output directory for the island area, perimeter, and surface area matrix files. If the specified output directory doesn't already exist, PleistoDist will create the output directory.

Value

This function outputs three matrices of island shape estimates in long format, with one column per interval in each matrix.

Examples

#create temp directory
path <- file.path(tempdir())
#create points shapefile
points <- sf::st_multipoint(rbind(c(179.41256,-17.79426), c(179.27600,-17.97850)))
#convert points to feature geometry
points <- sf::st_sfc(points)
points <- sf::st_cast(points, "POINT")
#set default projection (WGS84)
sf::st_crs(points) <- 4326
#save shapefile
sf::write_sf(points,paste0(path,"/points.shp"))
#load bathymetry file
fiji <- system.file("extdata","FJ.asc",package="PleistoDist")
#generate interval file for 1 interval and 20 kya cutoff time, binning by time
getintervals_time(time=20,intervals=1,outdir=path)
#generate maps based on interval file, projecting map using EPSG:3141
makemaps(inputraster=fiji,epsg=3141,intervalfile=paste0(path,"/intervals.csv"),outdir=path)
#calculate island shape, perimeter, and surface area, projecting points using EPSG:3141
pleistoshape_all(points=paste0(path,"/points.shp"),epsg=3141,
    intervalfile=paste0(path,"/intervals.csv"),mapdir=path,outdir=path)

g33k5p34k/PleistoDistR documentation built on Oct. 9, 2022, 5:27 a.m.