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Message-ID: <20100415123742.60050@gmx.net>
Date: 2010-04-15T12:37:42Z
From: Wilmar Igl
Subject: sum() returns 0 not NA

Dear all,

just a stupid R question, since the results puzzle me a bit:

> sum(c(NA,NA), na.rm=TRUE)
[1] 0
>  NA + NA   
[1] NA
> NA + 1
[1] NA
> 

Why does sum(c(NA,NA), na.rm=TRUE) return 0 and not NA?

Thanks in advance,

Will