R help - Jan 2005 - merge data frames taking mean/mode of multiple macthes

Hello :)

I have two data frames, one has properties taken on a
piece by piece basis and the other has performance on
a lot by lot basis. I wish to combine these two data
frames but the problem is that each lot has multiple
pieces and hence i need to take a mean of the
properties of multiple pieces and match it to the row
having data about the lot.

I was wondering if there is a simple commmand, an
extension of "merge", or an option of merge i do not
know which could easily do this work.

Thank you  :)

====I believe in equality for everyone, except reporters and photographers.
~Mahatma Gandhi

Dear Avneet

the function aggregate (see also ?aggregate) could be useful for
your problem. See the short example I've written below.

dat1 <- data.frame(lot = factor(1:10),y1 = rnorm(10))
str(dat1)
dat2 <- data.frame(nr = 1:100, lot = factor(rep(1:10, each = 10)),y2 =
rnorm(100))
str(dat2)

dat2.agr <- aggregate(dat2$y, by = list(lot = dat2$lot), FUN = mean)
names(dat2.agr)[2] <- "y2"

dat.mer <- merge(dat1, dat2.agr)
str(dat.mer)

Be careful about merging dataframes. There should always be a
control that the right cases are merged together.

Regards,

Christoph Buser

-- 
Christoph Buser <buser at stat.math.ethz.ch>
Seminar fuer Statistik, LEO C11
ETH (Federal Inst. Technology)	8092 Zurich	 SWITZERLAND
phone: x-41-1-632-5414		fax: 632-1228
http://stat.ethz.ch/~buser/


avneet singh writes:
 > Hello :)
 > 
 > I have two data frames, one has properties taken on a
 > piece by piece basis and the other has performance on
 > a lot by lot basis. I wish to combine these two data
 > frames but the problem is that each lot has multiple
 > pieces and hence i need to take a mean of the
 > properties of multiple pieces and match it to the row
 > having data about the lot.
 > 
 > I was wondering if there is a simple commmand, an
 > extension of "merge", or an option of merge i do not
 > know which could easily do this work.
 > 
 > Thank you  :)
 > 
 > ==== > I believe in equality for everyone, except reporters and
photographers.
 > ~Mahatma Gandhi
 > 
 > ______________________________________________
 > R-help at stat.math.ethz.ch mailing list
 > https://stat.ethz.ch/mailman/listinfo/r-help
 > PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html

-- 
Christoph Buser <buser at stat.math.ethz.ch>
Seminar fuer Statistik, LEO C11
ETH (Federal Inst. Technology)	8092 Zurich	 SWITZERLAND
phone: x-41-1-632-5414		fax: 632-1228
http://stat.ethz.ch/~buser/