> On Mar 21, 2018, at 9:58 AM, Jeff Newmiller <jdnew...@dcn.davis.ca.us> wrote: > > What do you mean by "should not"? > > NULL means "missing object" in R. The result of the sum function is always > expected to be numeric... so NA_real or NA_integer could make sense as > possible return values. But you cannot compute on NULL so no, that doesn't > work. > > See the note under the "Value" section of ?sum as to why zero is returned > when all inputs are removed.
But your perspective above that sentence is at odds with the note in the Details section of the same document: > sum(NULL) [1] 0 > ?sum starting httpd help server ... done > sum( integer(0) ) [1] 0 Best; David > -- > Sent from my phone. Please excuse my brevity. > > On March 21, 2018 9:03:29 AM PDT, Boris Steipe <boris.ste...@utoronto.ca> > wrote: >> Should not the result be NULL if you have removed the NA with >> na.rm=TRUE ? >> >> B. >> >> >> >>> On Mar 21, 2018, at 11:44 AM, Stefano Sofia >> <stefano.so...@regione.marche.it> wrote: >>> >>> Dear list users, >>> let me ask you this trivial question. I worked on that for a long >> time, by now. >>> Suppose to have a data frame with NAs and to sum some columns with >> rowSums: >>> >>> df <- data.frame(A = runif(10), B = runif(10), C = rnorm(10)) >>> df[1, ] <- NA >>> rowSums(df[ , which(names(df) %in% c("A","B"))], na.rm=T) >>> >>> If all the elements of the selected columns are NA, rowSums returns 0 >> while I need NA. >>> Is there an easy and efficient way to use rowSums within a function >> like >>> >>> function(x) ifelse(all(is.na(x)), as.numeric(NA), rowSums...)? >>> >>> or an equivalent function? >>> >>> Thank you for your help >>> Stefano >>> >>> >>> >>> (oo) >>> --oOO--( )--OOo---------------- >>> Stefano Sofia PhD >>> Area Meteorologica e Area nivologica - Centro Funzionale >>> Servizio Protezione Civile - Regione Marche >>> Via del Colle Ameno 5 >>> 60126 Torrette di Ancona, Ancona >>> Uff: 071 806 7743 >>> E-mail: stefano.so...@regione.marche.it >>> ---Oo---------oO---------------- >>> >>> ________________________________ >>> >>> AVVISO IMPORTANTE: Questo messaggio di posta elettronica può >> contenere informazioni confidenziali, pertanto è destinato solo a >> persone autorizzate alla ricezione. I messaggi di posta elettronica per >> i client di Regione Marche possono contenere informazioni confidenziali >> e con privilegi legali. Se non si è il destinatario specificato, non >> leggere, copiare, inoltrare o archiviare questo messaggio. Se si è >> ricevuto questo messaggio per errore, inoltrarlo al mittente ed >> eliminarlo completamente dal sistema del proprio computer. Ai sensi >> dell’art. 6 della DGR n. 1394/2008 si segnala che, in caso di necessità >> ed urgenza, la risposta al presente messaggio di posta elettronica può >> essere visionata da persone estranee al destinatario. >>> IMPORTANT NOTICE: This e-mail message is intended to be received only >> by persons entitled to receive the confidential information it may >> contain. E-mail messages to clients of Regione Marche may contain >> information that is confidential and legally privileged. Please do not >> read, copy, forward, or store this message unless you are an intended >> recipient of it. If you have received this message in error, please >> forward it to the sender and delete it completely from your computer >> system. >>> >>> -- >>> Questo messaggio stato analizzato da Libra ESVA ed risultato non >> infetto. >>> This message was scanned by Libra ESVA and is believed to be clean. >>> >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> 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. > > ______________________________________________ > 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. David Winsemius Alameda, CA, USA 'Any technology distinguishable from magic is insufficiently advanced.' -Gehm's Corollary to Clarke's Third Law ______________________________________________ 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.