[R] polygon shapefile from line edge coordinate list

[Murray Richardson]

Hello,

I am looking for advice on a task I am trying to complete.

I have a 4 column dataframe defining the start and end coordinates of 
line edges (from a CGAL alpha shapes function to define concave hulls 
from point clusters).  I would like to create polygon shapefiles from 
these line edges, presumably creating lines first and then polygons.

e.g. columns are:

startX  startY endX endY

where each row represents start and end coordinates of a line segment.

I am new to R spatial packages and I am not sure which one is best 
suited to this task. There seems to be a lot of options, which is great 
but hard to know which one to start with.  Any suggestions on the best 
way to proceed with this?  One further challenge is that the list 
includes line segments defining multiple polygons.

Thanks for any advice.

Murray