title: Why is the size of npy bigger than csv?
body: <p><a href="https://i.stack.imgur.com/jqNnz.png" rel="noreferrer"><img src="https://i.stack.imgur.com/jqNnz.png" alt="Screenshot"></a></p>
  
  <p>I changed csv to npy file. After the change, size of csv file is 5GB, and npy is 13GB.
  I thought a npy file is more efficient than csv.
  Am I misunderstanding this? Why is the size of npy bigger than csv?</p>
  
  <p>I just used this code</p>
  
  <pre><code>full = pd.read_csv('data/RGB.csv', header=None).values
  np.save('data/RGB.npy', full, allow_pickle=False, fix_imports=False)
  </code></pre>
  
  <p>and data structure like this:</p>
  
  <pre><code>R, G, B, is_skin
  2, 5, 1, 0
  10, 52, 242, 1
  52, 240, 42, 0
  ...(row is 420,711,257)
  </code></pre>