# Statistics for edges (lines) Extracts raster values for each edge and calculates specified statistics ```r graph.statistics(x, r, stats = c("min", "mean", "max"), buffer = NULL) ``` ## Arguments - `x`: sp SpatialLinesDataFrame or sf LINE object - `r`: A terra SpatRast or raster rasterLayer, rasterStack, rasterBrick object - `stats`: Statistics to calculate. If vectorized, can pass a custom statistic function. - `buffer`: Buffer distance, radius in projection units. For statistics based on edge buffer distance ## Returns data.frame object of statistics ## Note If the buffer argument is specified that, raster values within the specified buffer radius are extracted and included in the derived statistic(s). Else-wise, the statistics are derived from raster values that directly intersect each edge. ## Examples ```r library(sf) library(terra) data(ralu.site) xvars <- rast(system.file("extdata/covariates.tif", package="GeNetIt")) ( dist.graph <- knn.graph(ralu.site, row.names = ralu.site$SiteName, max.dist = 1500) ) skew <- function(x, na.rm = TRUE) { if (na.rm) x <- x[!is.na(x)] sum( (x - mean(x)) ^ 3) / ( length(x) * sd(x) ^ 3 ) } # Moments on continuous raster data system.time( { stats <- graph.statistics(dist.graph, r = xvars[[-6]], stats = c("min", "median", "max", "var", "skew")) } ) # Proportional function on nominal raster data p <- function(x) { length(x[x < 52]) / length(x) } system.time( { nstats <- graph.statistics(dist.graph, r = xvars[[6]], stats = "p") } ) # Based on 500m buffer distance around line(s) system.time( { stats <- graph.statistics(dist.graph, r = xvars[[-6]], stats = c("min", "median", "max", "var", "skew"), buffer = 500) } ) ``` ## Author(s) Jeffrey S. Evans and Melanie A. Murphy

graph.statistics function