Hi, If I do the following I can have a NULL in a list> x <- list( 1, list(3,NULL,4), 5 ) > x[[1]] [1] 1 [[2]] [[2]][[1]] [1] 3 [[2]][[2]] NULL [[2]][[3]] [1] 4 [[3]] [1] 5 This is a good thing for me as it can be passed through into C++ where I can know the value is missing. (Can't seem to detect a NA from C++ for some reason. There is RF_isNull in the API but no RF_isNA that I can find!) Is it possible to put a null in an already created list. e.g. now do> x[[2]][[2]] <- NULL > x[[1]] [1] 1 [[2]] [[2]][[1]] [1] 3 [[2]][[2]] [1] 4 [[3]] [1] 5 But x[[2]][[2]] has been deleted. Many thanks Regards, David
Charles C. Berry
2007-Dec-03 21:10 UTC
[R] Putting a NULL in a list (as cannot pass NA to C++)
On Mon, 3 Dec 2007, Rees, David wrote:> Hi, > > If I do the following I can have a NULL in a list > >> x <- list( 1, list(3,NULL,4), 5 ) >> x > [[1]] > [1] 1 > > [[2]] > [[2]][[1]] > [1] 3 > > [[2]][[2]] > NULL > > [[2]][[3]] > [1] 4 > > > [[3]] > [1] 5 > > This is a good thing for me as it can be passed through into C++ where I > can know the value is missing. (Can't seem to detect a NA from C++ for > some reason. There is RF_isNull in the API but no RF_isNA that I can > find!)Is this what you were looking for? Writing R Extensions 6.4 Missing and IEEE special values A set of functions is provided to test for NA, Inf, -Inf and NaN. These functions are accessed via macros: ISNA(x) True for R's NA only ISNAN(x) True for R's NA and IEEE NaN R_FINITE(x) False for Inf, -Inf, NA, NaN HTH, Chuck p.s. grep '<something>' within R's include directory can quickly resolve questions like this.> > Is it possible to put a null in an already created list. e.g. now do > >> x[[2]][[2]] <- NULL >> x > [[1]] > [1] 1 > > [[2]] > [[2]][[1]] > [1] 3 > > [[2]][[2]] > [1] 4 > > > [[3]] > [1] 5 > > > But x[[2]][[2]] has been deleted. > > Many thanks > > Regards, > David > > ______________________________________________ > R-help at 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. >Charles C. Berry (858) 534-2098 Dept of Family/Preventive Medicine E mailto:cberry at tajo.ucsd.edu UC San Diego http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901