Looking below and online, R's truth tables for NOT, AND, OR are identical to the NOT, AND, OR truth tables originating from Stephen Cole Kleene's "strong logic of indeterminacy", as demonstrated on the Wikipedia page entitled, "Three-Valued Logic"--specifically in the section entitled "Kleene and Priest Logics":
https://en.wikipedia.org/wiki/Three-valued_logic#Kleene_and_Priest_logics > > ttNOT <- cbind(c(FALSE, NA, TRUE), !c(FALSE, NA, TRUE)) > rownames(ttNOT) <- c("False", "na", "True") > colnames(ttNOT) <- c("A", "Not(A)") > ttNOT A Not(A) False FALSE TRUE na NA NA True TRUE FALSE > > ttAND <- outer(c(FALSE, NA, TRUE), c(FALSE, NA, TRUE), "&" ) > rownames(ttAND) <- c("False", "na", "True") > colnames(ttAND) <- c("False", "na", "True") > ttAND False na True False FALSE FALSE FALSE na FALSE NA NA True FALSE NA TRUE > > ttOR <- outer(c(FALSE, NA, TRUE), c(FALSE, NA, TRUE), "|" ) > rownames(ttOR) <- c("False", "na", "True") > colnames(ttOR) <- c("False", "na", "True") > ttOR False na True False FALSE NA TRUE na NA NA TRUE True TRUE TRUE TRUE > > The bottom section of the same Wikipedia page (section entitled "Application in SQL" ), and an additional Wikipedia page entitled "Null (SQL)" discusses how the Kleene logic described above is differentially implemented in SQL. https://en.wikipedia.org/wiki/Null_(SQL) HTH, Bill William Michels, Ph.D. On Sun, May 21, 2017 at 7:00 AM, Hadley Wickham <h.wick...@gmail.com> wrote: > On Fri, May 19, 2017 at 6:38 AM, S Ellison <s.elli...@lgcgroup.com> wrote: >>> TRUE & FALSE is FALSE but TRUE & TRUE is TRUE, so TRUE & NA could be >>> either TRUE or FALSE and consequently is NA. >>> >>> OTOH FALSE & (anything) is FALSE so FALSE & NA is FALSE. >>> >>> As I said *think* about it; don't just go with your immediate knee-jerk >>> (simplistic) reaction. >> >> Hmm... not sure that was quite fair to the OP. Yes, FALSE & <anything> == >> FALSE. But 'NA' does not mean 'anything'; it means 'missing' (see ?'NA'). It >> is much less obvious that FALSE & <missing> should generate a non-missing >> value. SQL, for example, generally takes the view that any expression >> involving 'missing' is 'missing'. > > That's not TRUE ;) > > sqlite> select (3 > 2) OR NULL; > 1 > > sqlite> select (4 < 3) AND NULL; > 0 > > Hadley > > > -- > http://hadley.nz > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
