st: Collpasing Data by every 4 observations

["Michael W. Beets" <beetsm@onid.orst.edu>]

I have 15sec interval data collected on individuals over the course of  
a single day.

The data look like the following, where "counts" are the primary  
outcome and time is the "time" (fraction of 24hrs) the counts occurred.

What I am attempting to do is create a mean of every 4 15sec intervals  
to reflect the average counts/min. Hence, if a person is monitored (at  
15sec intervals) over the duration of 1hr, they would have 240 lines  
of data containing counts. This needs to be collapsed into average  
counts/min (resulting in 60 lines of data/person).

However, I am unaware of how to specify the collapse command to take  
the average of every 4 lines of data.



. list  counts time  in 1/20

     +------------------+
     | counts      time |
     |------------------|
  1. |    210   .333507 |
  2. |     75   .333681 |
  3. |    166   .333854 |
  4. |    466   .334028 |
  5. |     29   .334201 |
     |------------------|
  6. |     19   .334375 |
  7. |     12   .334549 |
  8. |      0   .334722 |
  9. |      0   .334896 |
 10. |     16   .335069 |
     |------------------|
 11. |      0   .335243 |
 12. |    398   .335417 |
 13. |    566    .33559 |
 14. |      0   .335764 |
 15. |     10   .335938 |
     |------------------|
 16. |   1133   .336111 |
 17. |    651   .336285 |
 18. |    139   .336458 |
 19. |    393   .336632 |
 20. |    430   .336806 |
     +------------------+
r; t=0.03 12:03:12






Michael W. Beets, M.P.H., Ph.D.

Department of Public Health
Oregon State University
256 Waldo Hall
Corvallis, OR 97331-6406
PH:    541-738-2888
CELL:  541-231-6673
FAX:   541-737-4001
Email: beetsm@onid.orst.edu





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