Hi Alberto, It would help if you could provide a small example. I might break the problem down into three parts: 1) create a vector that has the final subgroupings you want 2) find the conditional means by subgroup 3) replicate the means as needed. My first guess would be start with:
"==" or "%in%" to compare or find levels from 2008 %in% 2009 by(Data, GroupingVar, FUN = mean) This is probably not the best way, but since "GroupingVar" should be a factor, I would be tempted to do: tmp <- (factor(GroupingVar, levels = levels(GroupingVar), labels = ResultsofByCall) YourMeans <- as.numeric(levels(tmp))[tmp] as a way to map the means back to their appropriate subcondition replicated as many times as necessary. I'm sure you will get more detailed help if you can post a bit of sample data. HTH, Josh On Thu, Nov 18, 2010 at 8:10 AM, albechan <alberto.case...@satt.biz> wrote: > > Hi guys, I have two data frames: one referred to 2008 and one to 2009. Their > structure is identical except for the different data in them. > I need to create a vector alfa of the same length of the dataframe 2009 and > fill each element with the mean of 2008$var1 conditional to the subgroup > indicated by a factor variable in 2009$var2. > In this case it would be easy to use the function > alfa[i]<-ave(2008$var1,2008$var2==2009$var2[i],FUN=mean). > The problem is that 2008$var2 and 2009$var2 contain both 20 levels each but > only 18 of them are shared. So for those 18 I need to find the result that > I`d get applying the above formula (which in any case doesnt work if the > levels are not identical in the two data frames colmns) and for those two > different levels in 2009$var2 to use the average of the whole column > 2008$var2. > Anybody has some ideas? Please help me... > Hope it`s clear enough what I need. > Thanks! > alberto > -- > View this message in context: > http://r.789695.n4.nabble.com/conditional-mean-between-two-data-frames-with-different-levels-tp3049010p3049010.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ 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.