You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: axisanglebetween.m
    path of file: ./repos/gptoolbox/mesh
    
    the code of the file until where you have to start completion: function [w,a,R] = axisanglebetween(u,v,nan_replacement)
  % AXISANGLEBETWEEN compute the axis and angle representation of the rotation
  % between two vectors
  %
  % [w,a] = axisanglebetween(u,v)
  % [w,a] = axisanglebetween(u,v,nan_replacement) same as above but NaN rows
  % resulting from angle exactly pi are replaced with nan_replacement
  %
  % Inputs:
  %   u  n by dim list of row vectors
  %   v  n by dim list of row vectors
  %   Optional:
  %     nan_replacement vector replacement for NaN rows in w
  % Outputs:
  %   w  n by 3 list of axis vectors, if dim = 2 then this is as if u v had 0s
  %     as z coordinates, NaNs may appear if angle is exactly pi

    
function [w,a,R] = axisanglebetween(u,v,nan_replacement)
  % AXISANGLEBETWEEN compute the axis and angle representation of the rotation
  % between two vectors
  %
  % [w,a] = axisanglebetween(u,v)
  % [w,a] = axisanglebetween(u,v,nan_replacement) same as above but NaN rows
  % resulting from angle exactly pi are replaced with nan_replacement
  %
  % Inputs:
  %   u  n by dim list of row vectors
  %   v  n by dim list of row vectors
  %   Optional:
  %     nan_replacement vector replacement for NaN rows in w
  % Outputs:
  %   w  n by 3 list of axis vectors, if dim = 2 then this is as if u v had 0s
  %     as z coordinates, NaNs may appear if angle is exactly pi
  %   a  n by 1 list of angles
  %
  % Copyright 2011, Alec Jacobson (jacobson@inf.ethz.ch)
  %

  assert(all(size(u) == size(v)));
  dim = size(u,2);
  assert((dim == 2) || (dim == 3));
  n = size(u,1);

  u = normalizerow(u);
  v = normalizerow(v);

  if(dim == 2)
    u = [u zeros(n,1)];
    v = [v zeros(n,1)];
  end