[O] calculating column averages

[Jude DaShiell]

In this case I don't want to tell org-mode how many rows to calculate, and 
I put a table together with an averages line in its own footer section.  I 
prefer when doing these things to output final averages and totals just 
under table headers then go down into detail records after that.  Could 
someone take a look at the following table and tell me how to get an 
average on column 2 of this table?
Cut here.

| Date Stamp             |         Systalic | Diastalic | Pulse |   |   |   |   
|   |   |   |
|------------------------+------------------+-----------+-------+---+---+---+---+---+---+---|
| [2011-07-19 Tue 02:26] |              138 |        92 |    74 |   |   |   |   
|   |   |   |
| [2011-07-21 Thu 03:50] |              128 |        79 |    76 |   |   |   |   
|   |   |   |
| [2011-07-20 Wed 04:03] |              130 |        85 |    74 |   |   |   |   
|   |   |   |
| [2011-07-22 Fri 02:33] |              121 |        80 |    79 |   |   |   |   
|   |   |   |
|                        |                  |           |       |   |   |   |   
|   |   |   |
|------------------------+------------------+-----------+-------+---+---+---+---+---+---+---|
| Averages               | $2=vmean(@<..@>) |           |       |   |   |   |   
|   |   |   |
|                        |                  |         - |       |   |   |   |   
|   |   |   |
|                        |                  |           |       |   |   |   |   
|   |   |   |
  
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