title: RANSAC estimating Affine transformation
body: <p>For a image mosaic application, I took the matches of the descriptors and stored it in a matrix matches 2xM. I now want to apply Ransac with affine, so i got my random sample with was 2x3 matrix, then i tried applying the code</p>
  
  <p>[tform,inlier1,inlier2] = estimateGeometricTransform(sample(1,:),sSample(2,:),'affine');</p>
  
  <p>This doesn't seem to work because it requires that my columns to be 2, transposing it to 3x2 doesnt work as well since for affine i need 3 points of correspondences.</p>
  
  <p>Matches also returns only the index of matched descriptors, how can I 
  extract its coordinates and apply it to my tform transformation?</p>
  
  <pre><code>[f,d] = vl_sift(image1);
  [f1,d2] = vl_sift(image2);
  [matches, scores] = vl_ubcmatch(d, d2) ;
  
  ranMatch = randperm(size(matches,2),3); 
  sample = matches(:,ranMatch);
  [tform,inlier1,inlier2] = 
  estimateGeometricTransform(sample(1,:),sample(2,:),'affine');
  </code></pre>