title: How can I create fastly, with numpy an asociation of two vectors, one for indices of the second and other for booleans?
body: <p>is my first question here, and I don't know how call it, so...</p>
  
  <p>I have a numpy vector of "groups" int, like:</p>
  
  <pre><code>g = [2, 4, 3, 2, 1, 1, 1, 2, 1, 3]
  </code></pre>
  
  <p>I have a numpy vector of "visible" boolean, like:</p>
  
  <pre><code>v = [True, False, True, False, False]
  </code></pre>
  
  <p>"v" has a size representing maximum number of groups (ex: 0 to 4)</p>
  
  <p>"g" has indices that can't exced the limits of "v" (ex: 0 to 4)
  but not necesarily has all the indices of "v" (ex: don't 0)
  in size "g" can be different to "v", like in exmple.</p>
  
  <p>so I need a new vector that pass booleans to "g" like:</p>
  
  <pre><code>b = [T, F, F, T, F, F, F, T, F, F]
  </code></pre>
  
  <p>I can make it with a for, but I need speed, some idea?</p>