-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Benjamin Gillespie
Sent: Sunday, November 17, 2013 3:47 PM
To: r-help at r-project.org
Subject: [R] Extract values from vector and repeat by group
Hi all,
I hope you can help.
I have a data frame 'df':
group=c(rep(1,8),rep(2,10),rep(3,11))
var=rnorm(29)
time=c(seq(1,8),seq(1,10),seq(1,11))
df=data.frame(group,var,time)
I would like to extract the value from 'var' for each 'group' at
'time'=4 and repeat these extracted values in a new vector ('new') n
times where n is the number of rows for each group. I did this by hand
as below, but there must be a quicker way:
subset=subset(df,df$time==4)
subset
group var time
4 1 0.2531270 4
12 2 -0.3600128 4
22 3 0.4194730 4
df$new=c(rep(0.2531270,8),rep(-0.3600128,10),rep(0.4194730,11))
Any questions please ask,
Many thanks in advance,
Ben Gillespie, Research Postgraduate
o-------------------------------------------------------------------o
School of Geography, University of Leeds, Leeds, LS2 9JT o-------------
------------------------------------------------------o
Tel: +44(0)113 34 33345
Mob: +44(0)770 868 7641
o-------------------------------o
http://www.geog.leeds.ac.uk/
o-------------------------------------o
@RiversBenG
o--------------o