From murdoch at stats.uwo.ca  Wed Aug 22 19:16:44 2007
From: murdoch at stats.uwo.ca (Duncan Murdoch)
Date: Wed, 22 Aug 2007 13:16:44 -0400
Subject: [Rd] paste() with NAs ..  change worth persuing?
In-Reply-To: <18124.23379.575814.316093@stat.math.ethz.ch>
References: <18124.23379.575814.316093@stat.math.ethz.ch>
Message-ID: <46CC6F7C.2010600@stats.uwo.ca>

On 8/22/2007 11:50 AM, Martin Maechler wrote:
> Consider this example code
> 
>  c1 <- letters[1:7]; c2 <- LETTERS[1:7]
>  c1[2] <- c2[3:4] <- NA
>  rbind(c1,c2)
> 
>   ##   [,1] [,2] [,3] [,4] [,5] [,6] [,7]
>   ## c1 "a"  NA   "c"  "d"  "e"  "f"  "g" 
>   ## c2 "A"  "B"  NA   NA   "E"  "F"  "G" 
> 
>   paste(c1,c2)
> 
>   ## -> [1] "a A"  "NA B" "c NA" "d NA" "e E"  "f F"  "g G" 
> 
> where a more logical result would have entries 2:4 equal to
>       NA 
> i.e.,  as.character(NA)
> aka    NA_character_
> 
> Is this worth persuing, or does anyone see why not?

A fairly common use of paste is to put together reports for human 
consumption.  Currently we have

 > p <- as.character(NA)
 > paste("the value of p is", p)
[1] "the value of p is NA"

which looks reasonable. Would this become

 > p <- as.character(NA)
 > paste("the value of p is", p)
[1] NA

under your proposal?  (In a quick search I was unable to find a real 
example where this would happen, but it would worry me...)

Duncan Murdoch



[Rd] paste() with NAs .. change worth persuing?
Duncan Murdoch