[R] Make package out of own function

[Johannes Radinger]

Hello,

I already posted that on stackoverflow[1], but although it's crossposting,
I think this question can probably easier to be answered by other R-users on this list, which maintain packages etc.

I would like to make a package out of a function. The function
is working in a script, but when I install and load it as library()
I get an error. The example-function is:

#Make generic function
f <- function(x,...) UseMethod("f")

#Default method
f.default <- function(a,b=5,c=3,...){
	out <- a+b+c
	class(out) <- "f"
	out
}

# Print method
print.f <- function(x,...){
	cat("Result for f: ")
	print(unclass(x))
}

In the NAMESPACE for export I set "f".
When I try to run the function from the package I get: 
Error in UseMethod("f") : 
  no applicable method for 'f' applied to an object of class "c('double', 'numeric')"

here some additional info:
> sessionInfo()
R version 2.14.2 (2012-02-29)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

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

other attached packages:
[1] fishmove_0.0-1 plyr_1.7.1     ggplot2_0.9.0 

loaded via a namespace (and not attached):
 [1] colorspace_1.1-1   dichromat_1.2-4    digest_0.5.1       grid_2.14.2        MASS_7.3-17       
 [6] memoise_0.1        munsell_0.3        proto_0.3-9.2      RColorBrewer_1.0-5 reshape2_1.2.1    
[11] scales_0.2.0       stringr_0.6       
> 


Can anyone explain me how to solve that resp. how to make my own function into a package?

Best regards,

Johannes

[1]: http://stackoverflow.com/questions/8430178/arguments-and-classes-for-writing-generic-functions-in-r

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