make.systematic {secr} | R Documentation |
A rectangular grid of clusters within a polygonal region.
make.systematic(n, cluster, region, spacing = NULL, origin = NULL, originoffset = c(0,0), chequerboard = c('all','black','white'), ...)
n |
integer approximate number of clusters (see Details) |
cluster |
traps object defining a single cluster |
region |
dataframe or SpatialPolygonsDataFrame with coordinates of perimeter |
spacing |
scalar distance between cluster centres |
origin |
vector giving x- and y-cooordinates of fixed grid origin (origin is otherwise random) |
originoffset |
numeric; 2-vector (x,y offsets); see Details |
chequerboard |
logical; if not ‘all’ then alternate clusters are omitted |
... |
arguments passed to |
region
may be any shape. The sp class
SpatialPolygonsDataFrame is useful for complex shapes and input from
shapefiles using rgdal (see Examples). Otherwise,
region
should be a dataframe with columns ‘x’ and ‘y’.
spacing
may be a vector with separate values for spacing in x-
and y- directions. If spacing
is provided then n
is ignored.
If n
is a scalar, the spacing of clusters is determined from
the area of the bounding box of region
divided by the requested
number of clusters (this does not necessarily result in exactly n
clusters). If n
is a vector of two integers these are taken to be
the number of columns and the number of rows.
After preparing a frame of cluster centres, make.systematic
calls trap.builder
with method = ‘all’; ... allows the
arguments ‘rotation’, ‘edgemethod’, ‘plt’, and ‘detector’ to be
passed. Setting the trap.builder
arguments frame
,
method
, and samplefactor
has no effect.
If origin
is not specified then a random uniform origin is chosen within a box (width = spacing) placed with its bottom left corner at the bottom left of the bounding box of region
, shifted by originoffset
. Before version 3.1.8 the behaviour of make.systematic
was equivalent to originoffset = c(wx,wy)
where wx,wy
are the cluster half widths.
chequerboard = "black"
retains black ‘squares’ and chequerboard = "white"
retains white ‘squares’, where the lower left cluster in the candidate rectangle of cluster origins is black, as on a chess board. The effect is the same as increasing spacing by sqrt(2) and rotating through 45 degrees.
A single-session ‘traps’ object.
From 3.2.0 these additional attributes are set –
origin | coordinates of grid origin |
centres | coordinates of true cluster centres (cf cluster.centres ) |
originbox | vertices of rectangular spatial sampling frame for random origin |
Do not confuse with the simpler function make.grid
,
which places single detectors in a rectangular array.
trap.builder
, cluster.centres
,
readOGR
mini <- make.grid(nx = 2, ny = 2, spacing = 100) region <- cbind(x=c(0,2000,2000,0), y=c(0,0,2000,2000)) temp <- make.systematic(25, mini, region, plt = TRUE) temp <- make.systematic(c(6, 6), mini, region, plt = TRUE, rotation = -1) ## Example using shapefile "possumarea.shp" in ## "extdata" folder. By default, each cluster is ## a single multi-catch detector ## Not run: datadir <- system.file("extdata", package = "secr") possumarea <- rgdal::readOGR(dsn = datadir, layer = "possumarea") possumgrid <- make.systematic(spacing = 100, region = possumarea, plt = TRUE) ## or with 2 x 2 clusters possumgrid2 <- make.systematic(spacing = 300, cluster = make.grid(nx = 2, ny = 2, spacing = 100), region = possumarea, plt = TRUE, edgemethod = "allinside") ## label clusters text(cluster.centres(possumgrid2), levels(clusterID (possumgrid2)), cex=0.7) ## If you have GPSBabel installed and on the Path ## then coordinates can be projected and uploaded ## to a GPS with `writeGPS', which also requires the ## package `proj4'. Defaults are for a Garmin GPS ## connected by USB. writeGPS(possumgrid, proj = "+proj=nzmg") ## End(Not run)