It works. Thanks Jim. I guess this will be a "lots of coffee" morning kinda day.
jim holtman <[EMAIL PROTECTED]> wrote: 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 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? 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 and provide commented, minimal, self-contained, reproducible code.