% DOT DOT Dot Product Function
% 
% Usage
% 
% Computes the scalar dot product of its two arguments.  The general
% syntax for its use is
% 
%   y = dot(x,z)
% 
% where x and z are numerical vectors of the same length.  If 
% x and z are multi-dimensional arrays of the same size, then
% the dot product is taken along the first non-singleton dimension.
% You can also specify the dimension to take the dot product along using
% the alternate form
% 
%   y = dot(x,z,dim)
% 
% where dim specifies the dimension to take the dot product along.
function y = dot(x,z,dim)
  if (isvector(x) && isvector(z))
    if (numel(x) ~= numel(z))
      error('dot requires its arguments to be equal length');
    end
    y = x(:)'*z(:);
  else
    try
      q = x.*z;
    catch
      error('dot requires multi-dimensional arguments to be the same size and numeric');
    end
    if (~exist('dim'))
      y = sum(q);
    else
      y = sum(q,dim);
    end
  end