Plot a scale bar.
mf_scale(size, pos = "bottomright", lwd = 1.5, cex = 0.6, col, unit = "km")
size of the scale bar in units (default to km). If size is not set, an automatic size is used (1/10 of the map width)
position. It can be one of 'bottomright', 'bottomleft', 'interactive' or a vector of two coordinates in map units (c(x, y)).
width of the scale bar
cex of the text
units used for the scale bar. Can be "mi" for miles, "m" for meters, or "km" for kilometers (default)
No return value, a scale bar is displayed.
This scale bar is not accurate on unprojected (long/lat) maps.