[R] Function to find angle between coordinates?

[clair.crossupton at googlemail.com]

Dear all,

I was doing some self study and was wondering if a function already
exists which allows one to determine the angle between points.  e.g.
given the following (x,y) coordinates

input: (0,1); (0,0); (1,0)

would result in:

output: 90 degrees

Best regards
C.C.