The problem is that tapply is expecting a vector for the first argument, your first argument is a list or data frame, so the length that it sees is the number of list elements (columns of the data frame). You need to either pass a single vector, or use functions like aggregate or the plyr package to work on all the columns in a data frame.
-- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of RaoulD > Sent: Saturday, June 26, 2010 10:47 PM > To: r-help@r-project.org > Subject: Re: [R] Calculating Summaries for each level of a Categorical > variable > > > Hi Corey, > > Thanks so much for this. However, I get this error for tapply - "Error > in > tapply(RT, RT$R, fun=WA): > arguments must have same length". Any idea how to get around this? > > Thanks again, > Raoul > -- > View this message in context: > http://r.789695.n4.nabble.com/Calculating-Summaries-for-each-level-of- > a-Categorical-variable-tp2269349p2269815.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. ______________________________________________ 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.