On Mon, 25 Sep 2006, Bruce LaZerte wrote: > # R version 2.3.1 (2006-06-01) Debian Linux "testing" > > # Is the following behaviour a bug, feature or just a lack of > # understanding on my part? I see that this was discussed here > # last March with no apparent resolution.
Reference? It is the third alternative. A factor is sorted by its codes: consider > x <- factor(1:3, levels=as.character(3:1)) > x [1] 1 2 3 Levels: 3 2 1 > sort(x) [1] 3 2 1 Levels: 3 2 1 and that is what is happening here: for your example the levels of df$Date are > levels(df$Date) [1] "1970-04-04" "1970-08-11" "1970-10-18" "1970-06-04" "1970-08-18" so the result is sorted correctly. If you want to sort a character column in lexicographic order, don't make it into a factor. Similarly for a date column: use class "Date". > d <- as.factor(c("1970-04-04","1970-08-11","1970-10-18")) > x <- c(9,10,11) > ch <- data.frame(Date=d,X=x) > > d <- as.factor(c("1970-06-04","1970-08-11","1970-08-18")) > y <- c(109,110,111) > sp <- data.frame(Date=d,Y=y) > > df <- merge(ch,sp,all=TRUE,by="Date") > # the rows with dates missing all ch vars are tacked on the end. > # the rows with dates missing all sp vars are sorted in with > # the row with a date with vars from both ch and sp > # is.ordered(df$Date) returns FALSE > > # The rows of df are not sorted as they should be as sort=TRUE > # is the default. Adding sort=TRUE does nothing. > # So try this: > # dd <- df[order(df$Date),] > # But that doesn't work. > # Nor does sort(df$Date) > # But sort(as.vector(df$Date)) does work. > # As does order(as.vector(df$Date)), so this works: > dd <- df[order(as.vector(df$Date)),] > # ????? -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@stat.math.ethz.ch 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.