Andrija,
You should be able to extract the data that you want using a call like
this (AD substituted for your c)
with(AD, tapply(X2, X1, function(x) sort(x, dec=T)[1:5]))
That returns a list like this:
$`1`
[1] 10 9 8 7 6
$`2`
[1] 25 24 23 22 21
Just package it the way that you want.
Dave
From:
andrija djurovic <djandr...@gmail.com>
To:
r-help@r-project.org
Date:
12/10/2010 08:21 AM
Subject:
[R] (no subject)
Sent by:
r-help-boun...@r-project.org
Hi R-help,
I am trying to find a way to select five highest values in data frame
according some variable. I will demonstrate:
c
X1 X2
1 1 1
2 1 2
3 1 3
4 1 4
5 1 5
6 1 6
7 1 7
8 1 8
9 1 9
10 1 10
11 2 11
12 2 12
13 2 13
14 2 14
15 2 15
16 2 16
17 2 17
18 2 18
19 2 19
20 2 20
21 2 21
22 2 22
23 2 23
24 2 24
25 2 25
So I would like to select a rows with higest values of X2 inside X1.
Expected result should be:
X1 X2
1 10
1 9
1 8
1 7
1 6
2 25
2 24
2 23
2 22
2 21
I first oreded the data frame using
c=c[with(c,order(X1,-X2)),]
but I need a help to select highes five. It is easy to select when I have
just 2 unique values of X1 but what is if I have 500 unique values in X1?
Thanks
Andrija
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