What exactly are you trying to do? In the first case you are making a logical comparison and that is legal for "&". In the second you are trying to do a logical operation ("&") between two factors and that operation is not defined. This is what the error message is saying.
Also you first attempt is probably missing a comma: node1 <- data.trt[data.trt$stage=="1B" & data.trt$diameter=="=< 4", ] On Wed, Jun 4, 2008 at 8:10 AM, Philip Twumasi-Ankrah < [EMAIL PROTECTED]> wrote: > I am trying to define groupings from levels of factor variables and this > the warning message that R give > > "& not meaningful for factors". > > The nature of my task is this. I have a variable stage which has the levels > (1B, 2A, 2B) - these are the AJCC TNM stages of cancer, and another variable > diameter with factor levels ("=< 4", "4 - 6.5, > 6.5; limit values are > exclusive). > > I am trying to define series of groupings based on these variables and > others like them. > > My first attempts were; > > 1. node1 <- data.trt[data.trt$stage=="1B" & data.trt$diameter=="=< 4"] > 2. data.trt$stage[data.trt$stage=="1B"]& > data.trt$diameter[data.trt$diameter=="=< 4"] > > The second attempt was purely a fishing exercise. > > R gave me the waring message: > > Warning message: > In Ops.factor(data.trt$stage[data.trt$stage == "1B"], > data.trt$diameter[data.trt$diameter == : > & not meaningful for factors > > > My question is how do I get round this and by implication is there an > alternative way of defining a logical operation applicable to factors. > > Thanks already for the help. > > Philip > > > A Smile costs Nothing > > But Rewards Everything > > Happiness is not perfected until it is shared > -Jane Porter > > > > [[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<http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? [[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.