function z=vlinterp(k,z0,z)
% vlinterp - vectorial linear interpolation between points
%
% vlinterp :: 
%    real   ~'fraction of distance to travel from from initial to final point',
%    [Size] ~'initial point',
%    [Size] ~'final point'
% -> [Size] ~'interpolated point'.
%
% This returns a point (vector,array etc) on the straight line 
% between the given points.
%
% See also: LINTERP which treats each component independently.

z = z0+k*(z-z0);
