title: Whats an efficient way to filter an array based on a logical condition?
body: <p>let say i have a 3x6 array of doubles:</p>
  
  <p><em>double[][] arr</em> =  </p>
  
  <pre><code>            [1.2, 1,  1]
              [4.3, 1 , 1]
              [2.0, 1 , 1]
              [2.9, 1 , 1]
              [6.2, 1 , 1]
              [2.5, 1 , 1]
  </code></pre>
  
  <p>i want to return an array based on a tolerance of say x&lt;3.0 for the <strong><em>first column only</em></strong>.</p>
  
  <p>Which will return the full array minus the rows that dont match the condition (x&lt;3.0):</p>
  
  <p>I.E.</p>
  
  <p><em>double[][] returnArr</em> = </p>
  
  <pre><code>               [1.2, 1,  1]                   
                 [2.0, 1 , 1]
                 [2.9, 1 , 1]                   
                 [2.5, 1 , 1]
  </code></pre>
  
  <p>Whats an efficient way of accomplishing this (run time is a concern)???</p>