Uwe Ligges wrote: > Seth Falcon wrote: > > >>Uwe Ligges <[EMAIL PROTECTED]> writes: >> >> >> >>>Charles Dupont wrote: >>> >>> >>> >>>>I was messing around with R and I found an example R behaving oddly: >>>> >>>>a <- alist(NULL, "bob", c(3,6,2,3)) >>>>a >>>>a == 'NULL' >>>>a == "NULL" >>>>a == 'cat' >>>> >>> >>> >>>Always use is.null() to test on NULL, as in: >> >> >>What should I do if I want to check for the string "NULL"? > > > These are all dangerous, hence use the "safe" ways: > > sapply(a, is.null) > sapply(a, identical, "NULL") > sapply(a, is.na) > sapply(a, identical, "NA") > > Best, > Uwe
For the NA list problem. It would be better if 'as.character' when converting a list when it finds a NA value to set that element to the string NA value not "NA" the string. Charles > > >>>a <- list(NULL, "NULL", NA, "NA") >> >> >>>a == "NULL" >> >>[1] TRUE TRUE FALSE FALSE >> >> >> >>>a == "NA" >> >>[1] FALSE FALSE TRUE TRUE >> >>These are because of as.character: >> >> >> >>>as.character(a) >> >>[1] "NULL" "NULL" "NA" "NA" >> >>Yet, >> >> >> >>>as.character(NULL) >> >>character(0) >> >> >>>as.character(NA) >> >>[1] NA >> >> >>+ seth >> >>______________________________________________ >>R-devel@r-project.org mailing list >>https://stat.ethz.ch/mailman/listinfo/r-devel > > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Charles Dupont Computer System Analyst School of Medicine Department of Biostatistics Vanderbilt University ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
