Message-ID: <894643FDEA3A854A89B3E828737E2B1F0167A39D94F8@HERMES8.ds.leeds.ac.uk>
Date: 2013-11-17T14:47:03Z
From: Benjamin Gillespie
Subject: 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
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