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st: Selecting maximum values and generating sum variable


From   Catherine Tisch <catherine.tisch@canterbury.ac.nz>
To   statalist@hsphsun2.harvard.edu
Subject   st: Selecting maximum values and generating sum variable
Date   Tue, 24 May 2011 14:33:26 +1200

Hello

We have two issues that hopefully you can help us with:

1.	We want to select the highest UVI value per ID per day from five
hourly measurements.  It is possible for measurements to be zero and in
some instances data is missing.  An example of our dataset looks like:

ID	Day    Hour      	  UVI
1     1      11           5
1     1      12           9
1     1      13           7
1     1      14           3
1     1      15           4
1     2      11           7
1     2      12           8
1     2      13           2
1     2      14           1
1     2      15           .
1     3      11           1
1     3      12           2
1     3      13           1
1     3      14           1
1     3      15           0
2     1      11           .
2     1      12           .
2     1      13           .
2     1      14           .
2     1      15           .
2     2      11           9
2     2      12           10
2     2      13           10
2     2      14           8
2     2      15           6

We would like to create a new variable called 'UVPeak', from the example
above, the output would look like:

ID    Day    Hour         UVI      UVIPeak
1     1      11           5        9
1     1      12           9        9
1     1      13           7        9
1     1      14           3        9
1     1      15           4        9
1     2      11           7        8
1     2      12           8        8
1     2      13           2        8
1     2      14           1        8
1     2      15           .        8
1     3      11           1        2
1     3      12           2        2
1     3      13           1        2
1     3      14           1        2
1     3      15           0        2
2     1      11           .        .
2     1      12           .        .
2     1      13           .        .
2     1      14           .        .
2     1      15           .        .
2     2      11           9        10
2     2      12           10       10
2     2      13           10       10
2     2      14           8        10
2     2      15           6        10


2.	We want to know the sum of count of days per ID if UVIPeak is
not missing.  We will call this new variable 'SumDays'.  From the
example above, the output would look like:

ID    Day    Hour         UVI      UVIPeak     SumDays
1     1      11           5        9           3
1     1      12           9        9           3
1     1      13           7        9           3
1     1      14           3        9           3
1     1      15           4        9           3
1     2      11           7        8           3
1     2      12           8        8           3
1     2      13           2        8           3
1     2      14           1        8           3
1     2      15           .        8           3
1     3      11           1        2           3
1     3      12           2        2           3
1     3      13           1        2           3
1     3      14           1        2           3
1     3      15           0        2           3
2     1      11           .        .           1
2     1      12           .        .           1
2     1      13           .        .           1
2     1      14           .        .           1
2     1      15           .        .           1
2     2      11           9        10          1
2     2      12           10       10          1
2     2      13           10       10          1
2     2      14           8        10          1
2     2      15           6        10          1

Can anyone help us create these new variables?

Thanks in advance
Catherine

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