r - Making subclass of list -

r - Making subclass of list -

i have next code

obj <- list(list(a=4,f=5,g=5),list(a=44,f=54,g=54)) class(obj) <- "mysubclass" class(obj[1]) class(obj[2]) class(obj[1:2]) class(obj)

resulting in:

> class(obj[1]) [1] "list" > class(obj[2]) [1] "list" > class(obj[1:2]) [1] "list" > class(obj) [1] "mysubclass"

what proper solution not lose class subsetting? example, class(obj[1:2]) results in mysubclass , still behaves list.

the problem generic [ method stripping off class attribute. avoid this, define own generic mysubclass, i.e.

## reply suggested petr matousu ## based on simple.list method '[.mysubclass' = function(x, i, ...) { structure(nextmethod("["), class = class(x)) }

or

'[.mysubclass' = function(x, i, j, ..., drop=true) { ## store class attribute cl = class(x) ## pass object next method y = nextmethod('[') ## update class , homecoming class(y) = cl y }

your examples work expected. should at:

help('[') methods('[')

r r-s3