R help - Nov 2009 - Print methods

I've built a package that contains only two functions for a test run. They
are:

g <- function(x){
	x <- x^2
	class(x) <- "foo"
	x
}

print.foo <- function(x, ...){
	cat("This is a test:\n")
	cat(x, "\n")
	invisible(x)
	}

Simply testing these functions in the R workspace prior to a build yields:
> g(1:5)
This is a test:
1 4 9 16 25 

Now, I includes a NAMESPACE for this package, and it includes only the
following:

export(g)

Package build is now succesful. However, here is what occurs:
> library(foo)
> g(1:5)
[1]  1  4  9 16 25
attr(,"class")
[1] "foo"

Why is the attribute printed on screen here whereas this does not occur when the
function print.foo is simply sourced into the R workspace?

Thanks,
Harold
> sessionInfo()
R version 2.10.0 (2009-10-26) 
i386-pc-mingw32 

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] foo_1.0

Because print.foo is not defined if you only include the function "g"
in your namespace.



remko


-------------------------------------------------
Remko Duursma
Post-Doctoral Fellow

Centre for Plants and the Environment
University of Western Sydney
Hawkesbury Campus
Richmond NSW 2753

Dept of Biological Science
Macquarie University
North Ryde NSW 2109
Australia

Mobile: +61 (0)422 096908
www.remkoduursma.com



On Tue, Nov 10, 2009 at 8:14 AM, Doran, Harold <HDoran at air.org>
wrote:
> I've built a package that contains only two functions for a test run.
They are:
>
> g <- function(x){
> ? ? ? ?x <- x^2
> ? ? ? ?class(x) <- "foo"
> ? ? ? ?x
> }
>
> print.foo <- function(x, ...){
> ? ? ? ?cat("This is a test:\n")
> ? ? ? ?cat(x, "\n")
> ? ? ? ?invisible(x)
> ? ? ? ?}
>
> Simply testing these functions in the R workspace prior to a build yields:
>
>> g(1:5)
> This is a test:
> 1 4 9 16 25
>
> Now, I includes a NAMESPACE for this package, and it includes only the
following:
>
> export(g)
>
> Package build is now succesful. However, here is what occurs:
>
>> library(foo)
>> g(1:5)
> [1] ?1 ?4 ?9 16 25
> attr(,"class")
> [1] "foo"
>
> Why is the attribute printed on screen here whereas this does not occur
when the function print.foo is simply sourced into the R workspace?
>
> Thanks,
> Harold
>
>> sessionInfo()
> R version 2.10.0 (2009-10-26)
> i386-pc-mingw32
>
> locale:
> [1] LC_COLLATE=English_United States.1252
> [2] LC_CTYPE=English_United States.1252
> [3] LC_MONETARY=English_United States.1252
> [4] LC_NUMERIC=C
> [5] LC_TIME=English_United States.1252
>
> attached base packages:
> [1] stats ? ? graphics ?grDevices utils ? ? datasets ?methods ? base
>
> other attached packages:
> [1] foo_1.0
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>