Re: NA assignment for character vector

["Gezmu, Misrak (NIH/NIAID)" <MGEZMU@niaid.nih.gov>]

The is.na function is not doing its job. Until S-Plus fixes the problem, here is my suggestion. 
Copy the result of is.na to try.ok, then use "for" and "if" statements to assign "T" to the positions with "NA". try.ok has the results needed.

try<-c("a","b","c","NA","e")
> is.na(try)
[1] F F F F F
> try.ok<-is.na(try)
> for (i in 1:5) {if (try[i]=="NA") try.ok[i]<-T}
> try
[1] "a"  "b"  "c"  "NA" "e"
> try.ok
[1] F F F T F

-----Original Message-----
From: Sundar Dorai-Raj [mailto:sundar.dorai-raj@pdf.com]
Sent: Tuesday, February 25, 2003 11:55 AM
To: Stephen Lake
Cc: Splus Users Group
Subject: Re: [S] NA assignment for character vector

Stephen Lake wrote:
> Hi S-users,
>
> Could someone please tell me how I can assign NA's to
> character vectors and matrices? The usual element
> assignment does not seem to work. Here is an example:
>
>
>>vec <- letters[1:5]
>>vec
>
> [1] "a" "b" "c" "d" "e"
>
>>vec[4] <- NA
>>vec
>
> [1] "a" "b" "c" "NA" "e"
>
>>is.na(vec)
>
> [1] F F F F F
>
> If instead of letters[1:5] I assign the numeric vector
> 1:5, the behavior is as expected, ie the is.na() function
> detects a NA at position 4 of the vector.
>
> Any help would be greatly appreciated,
> Steve Lake
>
> PS I am using Version 6.0 Release 1 for Sun SPARC, SunOS 5.5
>
>

 From ?is.na:

REQUIRED ARGUMENTS:
x       an S-PLUS object, which should be logical, numeric, or complex.

WARNING:
This is always FALSE when x is of mode "character".

You should use == "NA" if x is character. As in:

 > vec <- letters[1:5]
 > vec[4] <- NA
 > vec == "NA"
[1] F F F T F

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