I think this is what you want: > MyVar <- 1:10 > MyVar [1] 1 2 3 4 5 6 7 8 9 10 > mean(MyVar) [1] 5.5 > txt <- "MyVar" > mean(txt) [1] NA Warning message: In mean.default(txt) : argument is not numeric or logical: returning NA > mean(get(txt)) [1] 5.5
------------------------------------- David L Carlson Department of Anthropology Texas A&M University College Station, TX 77840-4352 -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of John Posner Sent: Thursday, November 13, 2014 5:32 PM To: 'r-help@r-project.org' Subject: [R] Help with ddply/summarize I have a straightforward application of ddply() and summarize(): ddply(MyFrame, .(Treatment, Week), summarize, MeanValue=mean(MyVar)) This works just fine: Treatment Week MeanValue 1 MyDrug BASELINE 5.91 2 MyDrug WEEK 1 4.68 3 MyDrug WEEK 2 4.08 4 MyDrug WEEK 3 3.67 5 MyDrug WEEK 4 2.96 6 MyDrug WEEK 5 2.57 7 MyDrug WEEK 6 2.50 8 Placebo BASELINE 8.58 9 Placebo WEEK 1 8.25 ... But I want to specify the variable (MyVar) as a character string: ddply(MyFrame, .(Treatment, Week), summarize, MeanValue=mean("MyVar")) (Actually, the character string "MyVar" will be selected from a vector of character strings.) The code above produces no joy: Treatment Week MeanValue 1 MyDrug BASELINE NA 2 MyDrug WEEK 1 NA 3 MyDrug WEEK 2 NA 4 MyDrug WEEK 3 NA ... I tried a few things, including: as.name("MyVar") as.quoted("MyVar") ... but they all produced the name results: NAs I'm obviously thrashing around in the dark! Any advice would be greatly appreciated. -John [[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. ______________________________________________ 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.
