Message-ID: <OF31DC790B.162EEF49-ONC1257532.00366370-C1257532.00367F2C@precheza.cz>
Date: 2009-01-02T09:55:50Z
From: PIKAL Petr
Subject: Odp: the first and last observation for each subject
In-Reply-To: <54f7e7c30901020120p13b43319td7c00278d327e2ce@mail.gmail.com>
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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