Thanks for the invaluable help on my previous questions. The speed up in create
summary tables has been immense and I'm enthused about all the possibilities
going forward.
I'm currently stuck in trying to put together syntax for a "long" for table. In
the example below, each case is a unique Student by Year combination. What I'm
trying to do is take
such a table, aggregate on the student's current year (i.e., 2009 in this
data) SCHOOL_NUMBER, and calculate their mean score in the previous year (i.e.,
2008 in this data).
If the file were "wide", with each case representing a unique student with
separate variables for the year, then it would be easy to break on the 2009
SCHOOL_NUMBER and take the
mean of the 2008 SCORE.
Is conversion of long to wide necessary to do this?
STUDENT_ID SCHOOL_NUMBER YEAR SCORE
[1,] 1 100 2008 39
[2,] 1 200 2009 48
[3,] 2 100 2008 64
[4,] 2 200 2009 73
[5,] 3 100 2008 35
[6,] 3 200 2009 35
[7,] 4 100 2008 52
[8,] 4 200 2009 61
[9,] 5 100 2008 51
[10,] 5 200 2009 58
[11,] 6 300 2008 45
[12,] 6 400 2009 55
[13,] 7 300 2008 69
[14,] 7 400 2009 77
[15,] 8 300 2008 47
[16,] 8 400 2009 47
[17,] 9 300 2008 57
[18,] 9 400 2009 58
[19,] 10 300 2008 47
[20,] 10 400 2009 53
Thanks,
Damian
Damian Betebenner
Center for Assessment
PO Box 351
Dover, NH 03821-0351
Phone (office): (603) 516-7900
Phone (cell): (857) 234-2474
Fax: (603) 516-7910
[email protected]<mailto:[email protected]>
www.nciea.org<http://www.nciea.org/>
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