From alexhoward at nova.org.za  Wed Jan 11 11:33:18 2017
From: alexhoward at nova.org.za (Alex Ivan Howard)
Date: Wed, 11 Jan 2017 12:33:18 +0200
Subject: [Rd] R 'base' returning 0 as sum of NAs
Message-ID: <CAKvBZF2WBbUStVMowSjEv9hRTaR4YEKB=_mEVP=SKWjwsnzbOA@mail.gmail.com>

Dear R Team

The following line returns 0 (zero) as answer:
sum(c(NA_real_, NA_real_, NA_real_, NA_real_), na.rm = TRUE)

One would, however, have expected it to return 'NaN', as is the case with
function 'mean':

> mean(c(NA_real_, NA_real_, NA_real_, NA_real_), na.rm = TRUE)
[1] NaN

The problem in other words:
I have a vector filled with missing numbers. I run the 'sum' function on
it, but instruct it to remove all missing values first. Consequently, the
sum function is left with an empty numeric vector. There is nothing to sum
over, so it shouldn't actually be able to return a concrete numeric value?
Shouldn't it thus rather return either NA ('unknown'/'missing') or - in the
fashion of the mean function - NaN ('not a number')?

With the current state of affairs, the sum function poses the grave danger
of introducing zeros to one's data (and subsequently other values as well,
as soon as the zeros get taken up in further calculations).

I hope my e-mail finds you well and I wish the R team all of the best for
2017 :)

Kind regards

Alex I. Howard

Web: www.nova.org.za
Phone: +27 (0) 44 695 0749
VoiP: +27 (0) 87 751 3490
Fax:         +27 (0) 86 538 7958

	[[alternative HTML version deleted]]



[Rd] R 'base' returning 0 as sum of NAs
Alex Ivan Howard