get_map_border: Helper function to calculate the coordinate limits of map border
Description
Since the world map is huge, and flights are usually drawn in a relatively
small area, the map needs to be cropped based on the coordinates of airports
used. This function generates the coordinate limits of the cropped map.
Usage
get_map_border(v, type = c("long", "lat"), padding_ratio = 0.1)
Arguments
v
A double numeric vector - vector of longtitudes/latitudes.
type
A string - "long" or "lat". It indicates whether longtitudes or latitudes are input.
padding_ratio
A double number - 0 to 1. The padding ratio is defined as
padding / (maximum - minimum)