OD matrices often contain 'intrazonal' flows, where the origin is the same point as the
destination. This function can help identify such intrazonal OD pairs, using 2 criteria:
the total number of vertices (2 or fewer) and whether the origin and destination are the same.
Usage
is_linepoint(l)
Arguments
l
A spatial lines object
Details
Returns a boolean vector. TRUE means that the associated line is in fact a point
(has no distance). This can be useful for removing data that will not be plotted.