; docformat = 'rst'
;+
;This function returns the angle between two vectors, in radians.
;
; :Examples:
;   angle = vangle(vec_a, vec_b)
;-
;+
; :Params:
;   a : in, required, type=vector of double
;     First vector that will be used to calculate the angle.
;   b : in, required, type=vector of double
;     Second vector that will be used to calculate the angle.
;     
; :Returns:
;   Returns the angle between the two vectors, in radians.
;-
function vangle,a,b
  aa=normalize_grid(a)
  bb=normalize_grid(b)
  dp=dotp(aa,bb)
  
  return,acos(dp)
end