On 02/14/2012 08:43 AM, james.fo...@diamond.ac.uk wrote:
Dear R-developers community, I have the following generic:
setGeneric(
name="newsample",
def=function(x,y,z,a,b,c,...){standardGeneric("newsample")}
And I can build several methods for this generic. One useful thing is to use
"newsample"
with only one of the 6 arguments listed. At the moment this is what I do:
setMethod(
f="newsample",
signature=c("missing","missing","numeric","missing","missing","missing"),
function(x,y,z,a,b,c,...)
{
..............................
..............................
}
)
This would be used when the single argument is z:
newsample(z=12.5)
To use newsample with another argument (say x) I should implement the same as
before,
but with signature
c("numeric","missing","missing","missing","missing","missing").
Is there another shorter and easier way to do this?
Hi James --
A matter of opinion, but multiple dispatch like this can be very
complicated, e.g., figuring out the 'next' method when dispatching on
two or more arguments; I'd really discourage it.
A different approach, assuming that x, y, z, ... are all numeric() but
that the sample to be drawn differs, is to define a small class
hierarchy to be used for dispatch.
setClass("TypeOfSample")
setClass("XSample", contains="TypeOfSample")
XSample <- new("XSample") ## a 'singleton', used for dispatch
setClass("YSample", contains="TypeOfSample")
YSample <- new("YSample")
and then
setGeneric("newsample",
function(type, x=numeric(), ...) standardGeneric("newsample"),
signature="type")
setMethod("newsample", "XSample", function(type, x=numeric(), ...) {
"XSample"
})
setMethod("newsample", "YSample", function(type, x=numeric(), ...) {
"YSample"
})
One could implement a default method on "TypeOfSample", and use
callNextMethod() after initial transformation, if that were the pattern.
To use:
newsample(XSample, x=1:100)
Martin
J
--
Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109
Location: M1-B861
Telephone: 206 667-2793
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