Message-ID: <CA+dpOJnx=0bVNwyXW1n3RhYSzoMv8_QvQtbCbSpRxApd6-Bagw@mail.gmail.com>
Date: 2013-02-16T18:22:34Z
From: Christofer Bogaso
Subject: Handling NA values
In-Reply-To: <DADE97B5-97C3-430D-AB52-7F72549C2409@me.com>
Thanks Marc for your reply.
However this leads to my problem of handling rowSums() function (hence
colSums()). Let take following matrix:
> Mat <- matrix(c(1, 1, NA, -1, 1, NA, NA, 1, NA), nc = 3)
> Mat
[,1] [,2] [,3]
[1,] 1 -1 NA
[2,] 1 1 1
[3,] NA NA NA
> rowSums(Mat, na.rm = TRUE)
[1] 0 3 0
I want to have some way to distinguish the 1st '0' and the 3rd '0'. I
want to see NA directly for the 3rd. Any possibility how to do that
through the rowSum() function?
Thanks and regards,
On Sat, Feb 16, 2013 at 11:52 PM, Marc Schwartz <marc_schwartz at me.com> wrote:
>
> On Feb 16, 2013, at 11:55 AM, Christofer Bogaso <bogaso.christofer at gmail.com> wrote:
>
>> Hello again,
>>
>> I have a question on who sum() handle the NA values.
>>
>>> sum(c(NA, 1), na.rm = TRUE)
>> [1] 1
>>
>>
>> I understand this. However could not agree with following:
>>
>>> sum(c(NA, NA), na.rm = TRUE)
>> [1] 0
>>
>>
>> Where this '0' is coming from? Should not it be NA itself?
>>
>> Thanks and regards,
>
>
>
> The result of:
>
> sum(c(NA, NA), na.rm = TRUE)
>
> is to sum an empty set, hence the 0.
>
>
>> na.omit(c(NA, NA))
> logical(0)
> attr(,"na.action")
> [1] 1 2
> attr(,"class")
> [1] "omit"
>
>
>> sum(logical(0))
> [1] 0
>
>
> If you retained the NA's, then the result is undefined:
>
>> sum(c(NA, NA))
> [1] NA
>
>
> See:
>
> http://rwiki.sciviews.org/doku.php?id=tips:surprises:emptysetfuncs
>
> for more information.
>
> Regards,
>
> Marc Schwartz
>