This function orders the distance to neighboring polygons' centroids from nearest to farthest and returns a vector of integers.
rankGATdistance(area, nbdata, first, gatvars, mergevars)A spatial polygons data frame.
A data frame of (polygon) observations.
A data frame with one (polygon) observation.
A list of objects created by the GAT tool. It contains the strings myidvar, aggregator1, aggregator2, and boundary, which are all variables in the area, and the numbers minvalue1 and minvalue2. Both aggregator1 and aggregator2 must be numeric. The identifier, myidvar, must contain unique values.
A list of string objects needed to aggregate the areas in the GAT tool. It contains mergeopt1, mergeopt2, similar1, and similar2. The valid options for mergeopt1 and mergeopt2 are "closest", "least", and "similar". If "similar" is selected, similar1 and similar2 must be numeric variables in the area and similar2 cannot equal zero.
# add GAT variables
sf::st_agr(hftown) <- "constant"
centroids <- sf::st_coordinates(sf::st_geometry(sf::st_centroid(hftown)))
colnames(centroids) <- c("GATx", "GATy")
my_data <- data.frame(hftown, centroids)
my_data <- sf::st_as_sf(my_data, coords = c("GATx", "GATy"),
crs = sf::st_crs(hftown))
first <- my_data[which(grepl("37374", my_data$ID)), ] # only one observation
# hard coded for simplicity; use spdep::poly2nb() to get these obs
nbdata <- my_data[which(grepl("43412|02572|40794|79059", my_data$ID)), ]
# only adjacent neighbors to first
gatvars <- list(
myidvar = "ID", # character variable of unique values
aggregator1 = "TOTAL_POP", # numeric variable
aggregator2 = "TOTAL_POP", # numeric variable
minvalue1 = 5000, minvalue2 = 5000,
boundary = "COUNTY" # character variable of non-unique values
)
mergevars <- list(
mergeopt1 = "similar", # can be similar, closest, or least
mergeopt2 = "closest", # if "similar" fails
similar1 = "B_TOT", # numeric variable
similar2 = "W_TOT" # numeric variable without any zeros
)
# rank the distances
my_rank_list <- rankGATdistance(area = hftown, nbdata = nbdata,
first = first, gatvars = gatvars,
mergevars = mergevars)