function z=linterp_d(k,z0,d)
% linterp_d - linear interpolation between two points
%
% linterp_d :: 
%    real   ~'fraction of distance to travel from from initial to final point',
%    [Size] ~'initial point',
%    [Size] ~'vector from initial to final point'
% -> [Size] ~'interpolated point'.
%
% Definition is linterp_d(k,z0,d) = linterp(k,z0,z0+d)
%
% See also: LINTERP, VLINTERP

z = z0+k.*d;
