R/distance.R

In SimInf: A Framework for Data-Driven Stochastic Disease Spread Simulations

## This file is part of SimInf, a framework for stochastic
## disease spread simulations.
##
## Copyright (C) 2015 Pavol Bauer
## Copyright (C) 2017 -- 2019 Robin Eriksson
## Copyright (C) 2015 -- 2019 Stefan Engblom
## Copyright (C) 2015 -- 2022 Stefan Widgren
##
## SimInf is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## SimInf is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program.  If not, see <https://www.gnu.org/licenses/>.

##' Create a distance matrix between nodes for spatial models
##'
##' Calculate the euclidian distances beween coordinates for all
##' coordinates within the cutoff.
##' @param x Projected x coordinate
##' @param y Projected y coordinate
##' @param cutoff The distance cutoff
##' @param min_dist The minimum distance to separate two nodes.  If
##'     the coordinates for two nodes are identical, the min_dist must
##'     be assigned or an error is raised.  Default is NULL i.e. to
##'     raise an error.
##' @return \code{dgCMatrix}
##' @export
##' @importFrom methods new
##' @examples
##' ## Generate a grid 10 x 10 and place one node in each cell
##' ## separated by 100m.
##' nodes <- expand.grid(x = (0:9) * 100, y = (0:9) * 100)
##' plot(y ~ x, nodes)
##'
##' ## Define the cutoff to only include neighbors within 300m.
##' d <- distance_matrix(x = nodes$x, y = nodes$y, cutoff = 300)
##'
##' ## View the first 10 rows and columns in the distance matrix
##' d[1:10, 1:10]
distance_matrix <- function(x, y, cutoff, min_dist = NULL) {
    .Call(SimInf_distance_matrix,
          as.numeric(x),
          as.numeric(y),
          as.numeric(cutoff),
          as.numeric(min_dist))
}