title: binarize a sparse matrix in python in a different way
body: <p>Assume I have a matrix like:</p>
  
  <pre><code>4 0 3 5
  0 2 6 0
  7 0 1 0
  </code></pre>
  
  <p>I want it binarized as:</p>
  
  <pre><code>0 0 0 0
  0 1 0 0
  0 0 1 0
  </code></pre>
  
  <p>That is set threshold equal to 2, any element greater than the threshold is set to 0, any element less or equal than the threshold(except 0) is set to 1.</p>
  
  <p>Can we do this on python's csr_matrix or any other sparse matrix?</p>
  
  <p>I know scikit-learn offer Binarizer to replace values below or equal to the threshold by 0, above it by 1.</p>