Tena koe Erynn Have you checked tapply and aggregate?
HTH .... Peter Alspach -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Erynn Call Sent: Monday, 10 March 2014 3:40 p.m. To: r-help@r-project.org Subject: [R] How to obtain a mean by more than one other variable I'm trying to create a new variable (meanABUNDHA) by obtaining a mean value *by* other variables. I surveyed birds (multiple species) at multiple sites and have multiple surveys within a REP (i.e. in example data below, SURVEY 55 and 57 are in REP 11). I need the mean ABUNDHA (pooling SURVEY) for each BIRD species by REP and by SITE. Below, I would average 0.77 and 0.15 for MALL in REP 11 at SITE 1 to get 0.46 meanABUNDHA. An example of my data are as follows, including the new variable I hope to create meanABUNDHA: SITE REP SURVEY BIRD ABUNDHA meanABUNDHA 1 11 57 MALL 0.77 0.46 1 11 55 MALL 0.15 0.46 1 12 58 MALL 0.14 0.14 1 2 58 BAEA 0.03 0.03 3 4 64 AMCR 0.22 0.45 3 5 65 AMCR 0.67 0.45 7 11 56 MALL 0.01 0.01 I'm not sure how to incorporate more than one "by="? data.all4[,mean(ABUNDHA),by= REP] #Add new column containing the by-REP mean of ABUNDHA data.all5<-data.all4[,ABUNDHAmean:=mean(ABUNDHA),by=REP] Thank you for any guidance!! [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list 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. The contents of this e-mail are confidential and may be ...{{dropped:14}} ______________________________________________ R-help@r-project.org mailing list 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.
