> data.frame()[]NULL data frame with 0 rows> data.frame()[FALSE]Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows> data.frame()[NULL]Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows Is this a bug? I wouldn't have expected the warning in the last two cases. Regards, Hadley
Sorry, a better example is:> data.frame(a=1)[FALSE]NULL data frame with 1 rows> data.frame(a=1)[NULL]NULL data frame with 1 rows vs> data.frame()[FALSE]Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows> data.frame()[NULL]Warning in is.na(nm) : is.na() applied to non-(list or vector) NULL data frame with 0 rows Hadley