Odp: the first and last observation for each subject
Hi r-help-bounces at r-project.org napsal dne 02.01.2009 10:20:23:
I have the following data ID x y time 1 10 20 0 1 10 30 1 1 10 40 2 2 12 23 0 2 12 25 1 2 12 28 2 2 12 38 3 3 5 10 0 3 5 15 2 ..... x is time invariant, ID is the subject id number, y is changing over
time.
I want to find out the difference between the first and last observed y value for each subject and get a table like
sapply(split(test$y, test$ID), function(x) tail(x, 1)-head(x,1)) I am leaving formating to the resulting table to you. Hint: aggregate Best regards Petr
ID x y 1 10 20 2 12 15 3 5 5 ...... Is there any easy way to generate the data set? [[alternative HTML version deleted]]
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