getMeanSD(xy)
maskarea(mask, sessnum = 1)
masklength(mask, sessnum = 1)
edist(xy1, xy2)
nedist(xy1, xy2, mask, inf = Inf, ...)transitiongetMeanSD, a dataframe with columns `x' and `y' and two
rows, mean and SD.For maskarea, the summed area of mask cells in hectares (ha).For masklength, the summed length of mask cells in kilometers (km).For edist and nedist, a matrix with dim = c(nrow(xy1), nrow(xy2)). getmeanSD is used by make.mask to standardize
mask coordinates.
For masklength the input should be a linear mask from secrlinear.
edist computes the Euclidean distance between each point in xy1
and each point in xy2. (This duplicates the functionality of `rdist'
in package fields).
nedist computes the non-Euclidean distance between each point
in xy1 and each point in xy2, in two dimensions. The calculation uses
gdistance (van Etten 2014; see also Csardi \& Nepusz 2006): a
transition layer is formed representing the connections between
adjacent points in mask. By default, points within a 16-point
neighbourhood are considered `adjacent'. Distances are obtained by
Dijkstra's (1959) algorithm as least cost paths through the graph of
all points in the mask.
nedist has some subtle options. If `mask' is missing then the
transition layer will be formed from `xy2'. If `mask' has a covariate
named `noneuc' then this will be used to weight distances. The ...
argument of nedist allows the user to vary arguments of
transition (defaults transitionFunction =
mean and directions = 16). Be warned this can lead to unexpected
results! Point pairs that are completely separated receive the
distance +Inf unless a finite value is provided for the argument
`inf'. See
secr-noneuclidean.pdf
for uses of nedist.
Dijkstra, E. W. (1959) A note on two problems in connexion with graphs. Numerische Mathematik, 1, 269--271.
Csardi, G. and Nepusz, T. (2006) The igraph software package for complex network research. *InterJournal* **1695**. http://igraph.org.
van Etten, J. (2014) gdistance: distances and routes on geographical grids. R package version 1.1-5. http://CRAN.R-project.org/package=gdistance