koch.m

function koch(pl,pr,level)
%KOCH    Recursively generated Koch curve.
%   KOCH(pl, pr, level) recursively generates a Koch curve,
%   where pl and pr are the current left and right endpoints and
%   level is the level of recursion.

if level == 0
  plot([pl(1),pr(1)],[pl(2),pr(2)],'b'); % Join pl and pr.
  hold on
else
  A = (sqrt(3)/6)*[0 1; -1 0];           % Rotate/scale matrix.

  pmidl = (2*pl + pr)/3;
  koch(pl,pmidl,level-1)                 % Left branch.

  ptop = (pl + pr)/2 + A*(pl-pr);
  koch(pmidl,ptop,level-1)               % Left mid branch.

  pmidr = (pl + 2*pr)/3;
  koch(ptop,pmidr,level-1)               % Right mid branch.

  koch(pmidr,pr,level-1)                 % Right branch.
end