R/simulate_ind.R

In maudqueroue/intercali: Intercalibration Des Différents Types De Suivis Aeriens

# Generated by fusen: do not edit by hand


#' Simulate individuals with a inhomogenous Poisson point process
#'
#' From an sf class density map `map_obj` (data.frame), an inohomogene Poisson point process is used to simulate the presence of individuals in the study area. The probability of presence of an individual is dependent on the density given by the map. 
#' @param map_obj Dataframe. Sf map with a colum containg density informations density_m
#' @param crs Numeric. Projection system.

#'
#' @importFrom glue glue
#' @importFrom assertthat assert_that
#' @importFrom dplyr mutate select filter
#' @importFrom sf st_centroid st_coordinates st_crs
#' @importFrom sp coordinates<- proj4string<- gridded<- CRS
#' @importFrom maptools as.im.SpatialGridDataFrame
#'
#' @return Dataframe. Indivduals with their coordinates associated.
#' @export

#' @examples
#' 
#' data(dataset_map)
#' 
#' ind <- simulate_ind(map_obj = dataset_map,
#'                     crs = 2154)
#' 
#' head(ind)
#' 
simulate_ind <- function(map_obj, crs){
  
  # Function checks
  
  
  assert_that(inherits(map_obj, "sf"))
  if (!all(c("density_m") %in% names(map_obj))) {stop("map_obj must contain `density_m` column. Verify your column names.")}
  assert_that(is.numeric(map_obj$density_m))
  

# Function 
#st_make_grid

  # Create grid
  grid <- map_obj %>%
    st_centroid() %>%
    mutate(X = st_coordinates(.)[,1],
           Y = st_coordinates(.)[,2]) %>%
    as.data.frame() %>%
    select("X","Y","density_m")
  
  
  # Convert in grid class
  coordinates(grid) <- ~ X + Y
  proj4string(grid) <- CRS(st_crs(crs)$proj4string)
  gridded(grid) <- TRUE
  X_grid <- maptools::as.im.SpatialGridDataFrame(grid)
  
  # Inhomogenous Poisson point process
  ppp <- spatstat.core::rpoispp(lambda = X_grid, drop = TRUE)
  sim_ind <- data.frame(x = ppp$x, y = ppp$y)
  
  # Possibility to add group size
  sim_ind <- sim_ind %>%
    mutate(size = 1)
  
  return(sim_ind)
  
  }