Generate a repeating sequence of longitude and latitude coordinates based on a period of rotation.
get_lonlat_seq(lon, lat, n.period = 360, n.frames = n.period)vector of arbitrary longitudes or starting longitude (starting point for constant globe rotation).
vector of arbitrary latitudes or fixed, repeating latitude.
intended length of the period.
intended number of frames in animation.
returns a list containing a longitude vector and a latitude vector.
lon and lat may be scalars or vectors. If scalar, lat is simply repeated n.frames times.
If scalar, lon is always treated as a starting longitude and a rotational sequence of longitudes is beginning from lon
is generated for a length equal to n.frames, repeating the sequence if necessary.
If lon or lat are vectors, it is assumed that predefined custom sequences of longitude and latitude have been provided,
so they are required to be of length n.period.
However long it takes to iterate through the custom coordinates sequence ought to define the period.
It also makes sense in this case for n.frames to remain equal to n.period if the custom sequence is not meant to be cyclical but rather a single pass.
After this check the custom vectors are simply bound in a list.