function prob_3_3
  
close all;  

Y = [ 0 1 1;
      1 0 -1;
      1 1 1;
      2 0 -1];
w0 = [ 1 1 1 ];

nIters = 50;
w(1,:) = w0;
for i=2:nIters,
  tmp1 = Y*(w(i-1,:)')-ones(4,1);
  f  = mean( tmp1.^2 );
  gf(1) = 0.5*( tmp1' * Y(:,1) );
  gf(2) = 0.5*( tmp1' * Y(:,2) );
  gf(3) = 0.5*( tmp1' * Y(:,3) );
  gfNorm = norm( gf );
  w(i,:) = w(i-1,:) - (1/gfNorm)*gf;
end
w

figure; imagesc( w ); colorbar;