DF2 <- read.table(textConnection("sid pid slope
+ 1.1 1.1 2
+ 1.1 4.1 3
+ 1.1 5.1 2
+ 2.1 5.1 3
+ 3.2 1.2 2
+ 3.2 1.7 3"), header = TRUE)
> tapply(DF2$slope, as.factor(DF2$pid), mean)
1.1 1.2 1.7 4.1 5.1
2.0 2.0 3.0 3.0 2.5
Could also wrap it in with(DF2, ....) to make it more readable and
compact. As testing shows that the as.factor() is not needed.
--
David Winsemius
On Mar 13, 2009, at 6:43 PM, Vedula, Satyanarayana wrote:
Hi,
I was hoping someone could help figure out how to write code for R
to do the below.
I have data that looks like below. Variables, sid and pid are
strings, slope is numeric. I need R to get me the mean of slopes for
all pid's nested within each sid if there are more than one pid's
nested within sid.
If there is only pid for a sid, like for 2.1 below, I want R to
write a 0.
In the data below, I want to get the mean of slopes for pid (1.1;
4.1; and 5.1) because they are nested within sid 1.1 and so on.
Thanks in advance for any suggestions.
Swaroop
sid pid slope
1.1 1.1 2
1.1 4.1 3
1.1 5.1 2
2.1 5.1 3
3.2 1.2 2
3.2 1.7 3
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
