R help - Mar 2018 - Sum of columns of a data frame equal to NA when all the elements are NA

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.
-- 
Sent from my phone. Please excuse my brevity.

On March 21, 2018 9:03:29 AM PDT, Boris Steipe <boris.steipe at
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.sofia at 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.sofia at regione.marche.it
>> ---Oo---------oO----------------
>> 
>> ________________________________
>> 
>> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu?
>contenere informazioni confidenziali, pertanto ? 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 ? il destinatario specificato, non
>leggere, copiare, inoltrare o archiviare questo messaggio. Se si ?
>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 necessit?
>ed urgenza, la risposta al presente messaggio di posta elettronica pu?
>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 at 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 at 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.

Surely the result of summation of non-existent values is not defined, is it not?
And since the NA values have been _removed_, there's nothing left to sum
over. In fact, pretending the the result in that case is zero would appear
audacious, no?

Cheers,
Boris 




> On Mar 21, 2018, at 12:58 PM, Jeff Newmiller <jdnewmil at
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.
> -- 
> Sent from my phone. Please excuse my brevity.
> 
> On March 21, 2018 9:03:29 AM PDT, Boris Steipe <boris.steipe at
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.sofia at 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.sofia at regione.marche.it
>>> ---Oo---------oO----------------
>>> 
>>> ________________________________
>>> 
>>> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu?
>> contenere informazioni confidenziali, pertanto ? 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 ? il destinatario specificato, non
>> leggere, copiare, inoltrare o archiviare questo messaggio. Se si ?
>> 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 necessit?
>> ed urgenza, la risposta al presente messaggio di posta elettronica pu?
>> 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 at 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 at 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.

No. The empty sum is zero. Adding it to another sum should not change it.
Nothing audacious about that. This is consistent; other definitions just cause
trouble.

-pd
> On 21 Mar 2018, at 18:05 , Boris Steipe <boris.steipe at utoronto.ca>
wrote:
> 
> Surely the result of summation of non-existent values is not defined, is it
not? And since the NA values have been _removed_, there's nothing left to
sum over. In fact, pretending the the result in that case is zero would appear
audacious, no?
> 
> Cheers,
> Boris 
> 
> 
> 
> 
> 
>> On Mar 21, 2018, at 12:58 PM, Jeff Newmiller <jdnewmil at
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.
>> -- 
>> Sent from my phone. Please excuse my brevity.
>> 
>> On March 21, 2018 9:03:29 AM PDT, Boris Steipe <boris.steipe at
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.sofia at 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.sofia at regione.marche.it
>>>> ---Oo---------oO----------------
>>>> 
>>>> ________________________________
>>>> 
>>>> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu?
>>> contenere informazioni confidenziali, pertanto ? 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 ? il destinatario specificato,
non
>>> leggere, copiare, inoltrare o archiviare questo messaggio. Se si ?
>>> 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
necessit?
>>> ed urgenza, la risposta al presente messaggio di posta elettronica
pu?
>>> 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 at 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 at 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 at 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.
-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

> On Mar 21, 2018, at 9:58 AM, Jeff Newmiller <jdnewmil at
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.steipe at
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.sofia at 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.sofia at regione.marche.it
>>> ---Oo---------oO----------------
>>> 
>>> ________________________________
>>> 
>>> AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu?
>> contenere informazioni confidenziali, pertanto ? 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 ? il destinatario specificato, non
>> leggere, copiare, inoltrare o archiviare questo messaggio. Se si ?
>> 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 necessit?
>> ed urgenza, la risposta al presente messaggio di posta elettronica pu?
>> 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 at 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 at 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 at 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