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st: choosing how to collapse very large datasets


From   Hind Sbihi <sbihi@interchange.ubc.ca>
To   statalist@hsphsun2.harvard.edu
Subject   st: choosing how to collapse very large datasets
Date   Thu, 21 Oct 2010 20:14:24 -0700 (PDT)

Hello stata users

 The data I have collected has physiological measurements (variables in col 3 to 7) collected at 256Hz while study participants listen to a song and give the song a rating (last column).
 Because of the chosen frequency we generated 256 observations per second.
Every study participant (n=50) listens to 45 second excerpt for each of 37 songs.
 The volume of the data set is simply overwhelming at this stage and I am considering different options for starting at least to visualize the data (e.g. rating vs. physiologic responses) before doing any analysis.
 
 My question is: how can I aggregate the data? 
 Collapse() seems to be the appropriate command but I am wondering which arguments should go in the command.
 Below is a snapshot of what the data looks like for the first song for one participant.
 
 time	songid          hr     hraccel         scr        dscr         emg    resprate    skintemp   rating 
 0        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
 .0039063        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.0078125        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.011719        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.015625        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.019531        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.023438        1   000063.73   -00000.87   000001.72   -00000.00   000003.49   000050.44   000028.15        4 
.027344        1   000063.73   -00000.87   000001.72   -00000.00   000003.48   000050.44   000028.15        4 
.03125        1   000063.73   -00000.87   000001.72   -00000.00   000003.48   000050.44   000028.15        4 
.035156        1   000063.73   -00000.87   000001.72   -00000.00   000003.48   000050.43   000028.15        4 
 
 Many thanks in advance for your suggestions.
 
 Hind

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