possible bug: NULL equality in lists.
I think it'd be more appropriate to use: sapply(a, "==", "NULL") or sapply(a, "==", "NA") for this case. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://www.med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message ----- From: "Seth Falcon" <sfalcon at fhcrc.org> To: <r-devel at stat.math.ethz.ch> Sent: Tuesday, March 07, 2006 4:37 PM Subject: Re: [Rd] possible bug: NULL equality in lists.
Uwe Ligges <ligges at statistik.uni-dortmund.de> 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"?
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
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