I probably did not explain my data clearly. I am starting with a dataframe with three columns:
redlognumb radiologist barrtotal where the entries in the variable radiologist are either 1 or 2, indicating which radiologist generated that barrtotal. All subjects had their X-ray read independently by both radiologists. So there are two rows for each subject. I want to convert it to this structure: redlognumb radiologist.1.barrtotal radiologist.2.barrtotal in which there is only one row for each subject. At any rate, in the meantime, I think I figured out that I was "melting" improperly, and I think I've got it now. Thanks. --Chris Christopher W. Ryan, MD SUNY Upstate Medical University Clinical Campus at Binghamton 40 Arch Street, Johnson City, NY 13790 cryanatbinghamtondotedu PGP public keys available at http://home.stny.rr.com/ryancw/ "If you want to build a ship, don't drum up the men to gather wood, divide the work and give orders. Instead, teach them to yearn for the vast and endless sea." [Antoine de St. Exupery] hadley wickham wrote: > On Tue, Jan 20, 2009 at 11:10 PM, Christopher W. Ryan > <cr...@binghamton.edu> wrote: >> I start with a dataframe called xrays. It contains scores on films from >> each of two radiologists. It is in "long" format. I used the reshape >> package to melt a data frame and then cast it into "wide" format, one >> line for each patient (identified by redlognumb) with scores from both >> radiologists for a given patient on the same line. >> >> I named the result of the casting xrays.data. It is an array. I'd like >> it to be a three-variable dataframe, with one column for scores from >> each of two radiologists, and one column for redlognumb (because I will >> then need to merge it with another dataframe that has a column named >> redlognumb.) As you can see below, the data.frame() function turns >> xrays.data into a two-variable dataframe. How can I get three columns >> (or variables) into my final dataframe? > > It sounds to me like this final data frame would just be equivalent to > your initial unmolten data. What's the difference? > > Hadley > > PS. The melt function takes an na.rm argument that will remove any > missing values. > >> Thanks. >> >> >>> head(xrays) >> redlognumb radiologis barrtotal >> 1 3 2 13 >> 2 4 2 16 >> 3 5 2 10 >> 4 6 2 11 >> 5 9 2 NA >> 6 10 2 NA >> >>> melted.xrays <- melt(xrays, id=c("redlognumb","radiologis")) >>> >>> head(melted.xrays <- na.omit(melt(xrays, >> id=c("redlognumb","radiologis")))) >> >> redlognumb radiologis variable value >> 1 3 2 barrtotal 13 >> 2 4 2 barrtotal 16 >> 3 5 2 barrtotal 10 >> 4 6 2 barrtotal 11 >> 7 1 1 barrtotal 11 >> 8 2 1 barrtotal 2 >>> cast(melted.xrays.2, redlognumb~radiologis~variable) >> radiologis >> redlognumb 1 2 >> 1 11 NA >> 2 2 NA >> 3 12 13 >> 4 16 16 >> 5 12 10 >> . . . cut off for brevity . . . >> >>> str(xrays.data) >> int [1:42, 1:2, 1] 11 2 12 16 12 13 18 8 19 14 ... >> - attr(*, "dimnames")=List of 3 >> ..$ redlognumb: Named chr [1:42] "1" "2" "3" "4" ... >> .. ..- attr(*, "names")= chr [1:42] "1" "2" "3" "5" ... >> ..$ radiologis: Named chr [1:2] "1" "2" >> .. ..- attr(*, "names")= chr [1:2] "1" "80" >> ..$ variable : Named chr "barrtotal" >> .. ..- attr(*, "names")= chr "1" >>> data.frame(xrays.data) >> X1.barrtotal X2.barrtotal >> 1 11 NA >> 2 2 NA >> 3 12 13 >> 4 16 16 >> 5 12 10 >> 6 13 11 >> 7 18 NA >> 8 8 NA >> . . . . cut off for brevity . . . >> >> >> -- >> Christopher W. Ryan, MD >> SUNY Upstate Medical University Clinical Campus at Binghamton >> 40 Arch Street, Johnson City, NY 13790 >> cryanatbinghamtondotedu >> PGP public keys available at http://home.stny.rr.com/ryancw/ >> >> "If you want to build a ship, don't drum up the men to gather wood, >> divide the work and give orders. Instead, teach them to yearn for the >> vast and endless sea." [Antoine de St. Exupery] >> >> ______________________________________________ >> 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.
