Hello Bruce, hope this is helpful.
id_unique(data$id)
for (i in 1:length(id))
{
datai_data[data$id==id[i],]
outi_apply(datai[1:3,],2,mean,na.rm=T)
if (i==1)
assign("out",outi,where=1) else
assign("out",rbind(out,outi),where=1)
}
Yuying
Gao, MD, PhD
Pharsight
Corporation
www.pharsight.com
-----Original
Message-----
From:
s-news-owner@lists.biostat.wustl.edu
[mailto:s-news-owner@lists.biostat.wustl.edu]On
Behalf Of Bruce Green
Sent: Monday, November 22, 2004
3:40 PM
To: s-news@lists.biostat.wustl.edu
Subject: [S] Data Extraction
Hi,
I have
a large dataset of 20000 rows that contains 180 individuals identified by a
unique identification number. There are 5 columns of data with health status
data in each column, and a different number of rows for each individual i.e. 5
rows for individual 1 and 20 rows for individual no. 2. I wish to extract the
data from the first 3 rows for each individual and then perform a data function
for each individual....i.e. what is the average blood pressure for individual 1
in the first 3 rows of their data?
I
cannot seem to do this easily...any suggestions?
Regards
Dr
Bruce Green