search for: assoociative

I have search the archive and I could not find what I need so I will try to ask the question here. I read a table in (read.table) a <- read.table(.....) The table has column names like DayOfYear, Quantity, and Category. The values in the row for Category are strings (characters). I want to get all of the rows grouped by Category. The number of unique category names could be around 50. Say

Does anyone know what could be causing the following error message on startup of R: Error in .addMethodFrom(def,argName[1],class[1],fromClass) : object "*tmp*" not found. I'm using R 1.7.0 and Windows 2000. This happened shortly after I installed 1.7.0. Once it occurs, R freezes. >From then on R will always freeze with this error message. I reinstalled 1.7.0 and it worked