title: split up a matrix in matrices by value of column nodes in R
body: <p>I have a matrix like this in R:</p>
  
  <pre><code>          [,1]        [,2]        [,3]         [,4]            [,5]   
  19992    -33.54971    23.35746    0.0000000    2.107680e+01    19980219
  19993    -33.54203    23.40079    0.0000000    2.107696e+01    19980219
  19994    -33.53453    23.44445    0.0000000    2.107713e+01    19980219
  19995    -33.52719    23.48840    0.0000000    2.107730e+01    19980219
  19996    -33.51965    23.53200    0.0000000    2.107746e+01    19980219
  19997    -33.51183    23.57565    0.0000000    2.107763e+01    19980219
  19998    -33.50446    23.61958    0.0000000    2.107780e+01    19980219
  19999    -33.49678    23.66313    0.0000000    2.107796e+01    19980219 
  </code></pre>
  
  <p>Its actually a lot bigger (2.000.000 rows) but I think that this example will do for my question.</p>
  
  <p>I want to extract all rows that have a value between e.g. -33.52... and -33.55... in the first column and create a new matrix of these extracted rows. </p>
  
  <p>The output matrix would than be for example:</p>
  
  <pre><code>19992    -33.54971    23.35746    0.0000000    2.107680e+01    19980219
  19993    -33.54203    23.40079    0.0000000    2.107696e+01    19980219
  19994    -33.53453    23.44445    0.0000000    2.107713e+01    19980219
  19995    -33.52719    23.48840    0.0000000    2.107730e+01    19980219
  </code></pre>
  
  <p>Some tips would be great!</p>