Generate travel time to nearest major city — calc

Aggregates the high-resolution global travel time raster to the PRIO-GRID structure. Users can specify the aggregation function to summarize travel time values within each PRIO-GRID cell.

Usage

calc_traveltime(aggregation_function)

Arguments

aggregation_function: Function or character string specifying the aggregation method (see details above)

Value

A SpatRaster object

Details

Supported aggregation functions include: "mean", "max", "min", "median", "sum", "modal", "any", "all", "prod", "which.min", "which.max", "table", "sd" (sample standard deviation), and "std" (population standard deviation). Users may also provide a custom function.

References

Nelson (2008). “Travel Time to Major Cities: A Global Map of Accessibility.” 2025-05-14.

Examples

if (FALSE) { # \dontrun{
# Aggregate global travel time using median
travel_time_median <- calc_traveltime(aggregation_function = "median")
terra::plot(travel_time_median, main = "PRIO-GRID Median Travel Time")

# Aggregate using maximum travel time
travel_time_max <- calc_traveltime(aggregation_function = "max")
terra::plot(travel_time_max, main = "PRIO-GRID Maximum Travel Time")
} # }