title: What are the differences between numpy arrays and matrices? Which one should I use?
body: <p>What are the advantages and disadvantages of each?</p>
  
  <p>From what I've seen, either one can work as a replacement for the other if need be, so should I bother using both or should I stick to just one of them?</p>
  
  <p>Will the style of the program influence my choice? I am doing some machine learning using numpy, so there are indeed lots of matrices, but also lots of vectors (arrays).</p>