R/plot_and_get.R
    map-sel-poly.RdClick the points that should be connected as polygon. Input ends with right click (see
grid::grid.locator()). Polygon will be drawn closed.
map.sel.poly(data, pch = 19, size = 0.3, ...)
sel.poly(pch = 19, size = 0.3, ...)hyperSpec object for plotting map or list returned by plot_map()
symbol to display the points of the polygon for sel.poly()
size for polygon point symbol for sel.poly()
further arguments for grid::grid.points() and
grid::grid.lines()
map.sel.poly: array of indices for points within the selected polygon
sel.poly: n x 2 matrix with the corner points of the polygon
map.sel.poly is a convenience wrapper for plot_map(), sel.poly,
and sp::point.in.polygon(). For customized plotting, the plot can be produced by
plot_map(), plot_voronoi() or levelplot(), and the result of
that plot command handed over to map.sel.poly, see the example below.
If even more customized plotting is required,sel.poly should be used (see example).