Construct Systematic Detector Design
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'),
order = c('x', 'y', 'xb', 'yb'), rotate = 0, centrexy =
apply(bbox(region),1,mean), keep.design = TRUE, ...)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 |
order |
character; sort order for clusters (see Details) |
rotate |
numeric; number of degrees by which to rotate entire design clockwise about centroid of region bounding box |
centrexy |
numeric; 2-vector for centre of rotation, if any |
keep.design |
logical; if TRUE then input argument values are retained |
... |
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.
Note the distinction between argument rotate and the trap.builder
argument rotation that is applied separately to each cluster.
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.
order determines the ordering of clusters in the resulting traps object. The options are a subset of those for ID argument of make.grid:
| Option | Sort order |
| x | column-dominant |
| y | row-dominant |
| xb | column-dominant boustrophedonical (alternate columns reversed) |
| yb | row-dominant boustrophedonical (alternate rows reversed) |
rotate rotates the array about the given centre (default is centroid of the bounding box of region). Rotation requires package maptools to have been installed; non-zero values otherwise result in a warning.
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 |
From 4.2.0 if keep.design is TRUE then the input argument values are retained in attribute ‘design’ (a list with first component function = 'make.systematic').
Do not confuse with the simpler function make.grid,
which places single detectors in a rectangular array.
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)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.