Hi all --- I've stumbled upon some pretty annoying behavior, and I'm curious how others may have gotten around it. When using subset(...) on a data frame that contains a custom S3 field, the class is dropped in the result:
> MyClass <- function(x) structure(x, class = "MyClass") > df <- data.frame(x = 1:10, y = 10:1) > df$x <- MyClass(df$x) > str(df) 'data.frame': 10 obs. of 2 variables: $ x:Class 'MyClass' int [1:10] 1 2 3 4 5 6 7 8 9 10 $ y: int 10 9 8 7 6 5 4 3 2 1 > str(subset(df, x %% 2 == 0)) 'data.frame': 5 obs. of 2 variables: $ x: int 2 4 6 8 10 $ y: int 9 7 5 3 1 And so, any generic functions hooked to MyClass suddenly don't work on the subset results, but do work on the original data frame. I think I could write a custom as.data.frame.MyClass for all such classes, but this is annoying, indeed (and I don't know for sure if that's a robust solution) Wrapping in I(...) doesn't work, either: > df <- data.frame(x = 1:10, y = 10:1) > df$x <- I(MyClass(df$x)) > str(df) 'data.frame': 10 obs. of 2 variables: $ x:Classes 'AsIs', 'MyClass' int [1:10] 1 2 3 4 5 6 7 8 9 10 $ y: int 10 9 8 7 6 5 4 3 2 1 > str(subset(df, x %% 2 == 0)) 'data.frame': 5 obs. of 2 variables: $ x:Class 'AsIs' int [1:5] 2 4 6 8 10 $ y: int 9 7 5 3 1 (note that while 'AsIs' is kept, 'MyClass' has been removed in $x) Cheers! -Murat ______________________________________________ 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.
