You have several options. 1. You could use the aggregate function. If your data frame is called DF, you could do something like
with(DF, aggregate(Length, list(Identifier), mean)) 2. You could use the dplyr package like this library(dplyr) summarize(group_by(DF, Identifier), mean(Length)) Hope this is helpful, Dan Daniel Nordlund, PhD Research and Data Analysis Division Services & Enterprise Support Administration Washington State Department of Social and Health Services > -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Matthew > Sent: Tuesday, May 24, 2016 12:47 PM > To: r-help@r-project.org > Subject: [R] identify duplicate entries in data frame and calculate mean > > I have a data frame with 10 columns. > In the last column is an alphaneumaric identifier. > For most rows, this alphaneumaric identifier is unique to the file, however > some of these alphanemeric idenitifiers occur in duplicate, triplicate or > more. > When they do occur more than once they are in consecutive rows, so when > there is a duplicate or triplicate or quadruplicate (let's call them > multiplicates), > they are in consecutive rows. > > In column 7 there is an integer number (may or may not be unique. does not > matter). > > I want to identify each multiple entries (multiplicates) occurring in column > 10 > and then for each multiplicate calculate the mean of the integers column 7. > > As an example, I will show just two columns: > Length Identifier > 321 A234 > 350 A234 > 340 A234 > 180 B123 > 198 B225 > > What I want to do (in the above example) is collapse all the A234's and report > the mean to get this: > Length Identifier > 337 A234 > 180 B123 > 198 B225 > > > Matthew > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
