POSIXlt matching bug

x <- as.POSIXlt(Sys.Date())
names(x)

z <- as.POSIXct(Sys.Date())
x <- as.POSIXct(Sys.Date())
z==x

match(z,x)

z %in% x

-----Original Message-----
From: r-devel-bounces at r-project.org 
[mailto:r-devel-bounces at r-project.org] On Behalf Of McGehee, Robert
Sent: 29 June 2010 15:46
To: R-bugs at r-project.org; r-devel at r-project.org
Subject: [Rd] POSIXlt matching bug

I came across the below mis-feature/bug using match with 
POSIXlt objects
(from strptime) in R 2.11.1 (though this appears to be an old issue).

x <- as.POSIXlt(Sys.Date())
table <- as.POSIXlt(Sys.Date()+0:5)
length(x)

[1] 1

x %in% table  # I expect TRUE

[1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE

match(x, table) # I expect 1

[1] NA NA NA NA NA NA NA NA NA

This behavior seemed more plausible when the length of a 
POSIXlt object
was 9 (back in the day), however since the length was redefined, the
length of x no longer matches the length of the match function output,
as specified by the ?match documentation: "A vector of the same length
as 'x'".

I would normally suggest that we add a POSIXlt method for match that
converts x into POSIXct or character first. However, match does not
appear to be generic. Below is a possible rewrite of match 
that appears
to work as desired.

match <- function(x, table, nomatch = NA_integer_, 
incomparables = NULL)

    .Internal(match(if(is.factor(x)||inherits(x, "POSIXlt"))
as.character(x) else x,
                    if(is.factor(table)||inherits(table, "POSIXlt"))
as.character(table) else table,
                    nomatch, incomparables))

That said, I understand some people may be very sensitive to the speed
of the match function, and may prefer a simple change to the ?match
documentation noting this (odd) behavior for POSIXlt. 

Thanks, Robert

R.version
               _                            
platform       x86_64-unknown-linux-gnu     
arch           x86_64                       
os             linux-gnu                    
system         x86_64, linux-gnu            
status                                      
major          2                            
minor          11.1                         
year           2010                         
month          05                           
day            31                           
svn rev        52157                        
language       R                            
version.string R version 2.11.1 (2010-05-31)

Robert McGehee, CFA
Geode Capital Management, LLC
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