function rad = km2rad(km,radius)

%KM2RAD Converts distances from kilometers to radians
%
%  rad = KM2RAD(km) converts distances from kilometers to radians.
%  A radian of distance is measured along a great circle of a sphere.
%
%  rad = KM2RAD(km,radius) uses the second input to determine the
%  radius of the sphere.  If radius is a string, then it is evaluated
%  as an ALMANAC body to determine the spherical radius.  If numerical,
%  it is the radius of the desired sphere in kilometers.  If omitted,
%  the default radius of the Earth is used.
%
%  See also RAD2KM, KM2DEG, KM2NM, KM2SM, DISTDIM

%  Copyright 1996-1998 by Systems Planning and Analysis, Inc. and The MathWorks, Inc.
%  Written by:  E. Brown, E. Byrns
%   $Revision: 1.8 $    $Date: 1998/08/10 17:47:51 $


if nargin==0
	error('Incorrect number of arguments')
elseif nargin == 1
    radius = almanac('earth','radius','km');
elseif nargin == 2 & isstr(radius)
	radius = almanac(radius,'radius','km');
end

if max(size(radius)) ~= 1
     error('Scalar radius required')
elseif any([~isreal(km) ~isreal(radius)])
     warning('Imaginary parts of complex DISTANCE and/or RADIUS arguments ignored')
     km = real(km);   radius = real(radius);
end

rad = km/radius;