Hi > > > Specifically, since it has only a single detection indicator column > > (ceneq1), it implies that within any single sample either all the analytes > > were detected, or all were not. Not what I would expect. > > Don, > > I have been thinking about this and wondered whether the cast format was > appropriate just for the reason there's only a single censored indicator. > I'm glad you confirmed this as the/one problem. > > > As to your larger question of which layout is appropriate for use with > > NADA functions, the answer is that either can be used. The "trick" is to > > use the appropriate syntax to extract the values needed to pass the data > > to a NADA function. > > And I've not discovered this in the time I spent trying different syntax. > > > For the long format you subset the rows, then pass the appropriate > > columns. Here's one way: > > > > with(subset(chem, param=='AgDis') , ros(quant,ceneq1)) > > This makes a lot of sense. I was thinking that I needed to create separate > data frames for each parameter but subsetting on the fly is much more > efficient and elegant. > > > Hope this helps. > > It certainly does! Thanks. > > > (p.s., I still think you'll be better off in the long run if you store > > site, param, and maybe era, as character objects, not factors.) > > I need to research this because I thought that factors were character > objects used to partition quantities into groups.
It is partly a matter of opinion. I personally prefer factors as they seems to me handier. > a<-sample(letters[1:5], 20, replace=T) > a [1] "c" "e" "c" "d" "c" "d" "b" "d" "d" "d" "b" "a" "d" "b" "c" "e" "e" "c" "c" [20] "c" Suppose I want to change all "c" and "b" to "f" > a.f<-as.factor(a) > a.f [1] c e c d c d b d d d b a d b c e e c c c Levels: a b c d e > levels(a.f) [1] "a" "b" "c" "d" "e" In factors I can only change appropriate levels. > levels(a.f)[2:3]<-"f" > a.f [1] f e f d f d f d d d f a d f f e e f f f Levels: a f d e Regards Petr > > Regards, > > Rich > > ______________________________________________ > 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.