title: MATLAB: extracting groups of columns into a submatrix?
body: <p>I have a data-set, in which I want to extract columns 1-3, 7-9, 13-15, all the way to the end of the matrix</p>
  
  <p>As an example, I've used the standard magic function to create a matrix</p>
  
  <p>A=magic(10)</p>
  
  <p>A =</p>
  
  <pre><code>92    99     1     8    15    67    74    51    58    40
  98    80     7    14    16    73    55    57    64    41
   4    81    88    20    22    54    56    63    70    47
  85    87    19    21     3    60    62    69    71    28
  86    93    25     2     9    61    68    75    52    34
  17    24    76    83    90    42    49    26    33    65
  23     5    82    89    91    48    30    32    39    66
  79     6    13    95    97    29    31    38    45    72
  10    12    94    96    78    35    37    44    46    53
  11    18   100    77    84    36    43    50    27    59
  </code></pre>
  
  <p>I know that I can extract single columns starting at 1, in intervals of 3 with the command:</p>
  
  <p>Aex=a(:,1 : 3 : end)</p>
  
  <p>Aex =</p>
  
  <pre><code>92     8    74    40
  98    14    55    41
   4    20    56    47
  85    21    62    28
  86     2    68    34
  17    83    49    65
  23    89    30    66
  79    95    31    72
  10    96    37    53
  11    77    43    59
  </code></pre>
  
  <p>Say I want to extract groups of columns instead (e.g. column 1-3, 7-9 etc.).</p>
  
  <p>Is there a way to do this without having to manually point out all the column numbers?</p>
  
  <p>Thanks for your help!
  Rasmus</p>