Dear R-devel,
I've created an S4 class called "range.vec", which is meant to hold a
sequence of numbers, like one you would create using seq(). I'm trying to
only store a chunk of the sequence at any given time, to save memory. this
means that my class has slots for start, end, and step, as well as a cached
chunk slot and a slot for where the chunk is indexed within the complete
sequence vector.
I have functional get() and set() methods for chunking, along with '[',
'length', '[[', and 'el', and the class inherits from "numeric". However,
when I try to use a numeric method like 'mean', the function returns NaN
(other numeric methods output different errors).
>From debugging, I've learned that methods like "mean" are successfully
accessing my range.vec methods, but since there is no data stored in .Data,
the functions can't run correctly. I want the numeric methods to use my
chunking functions to access the data, but even after extensive searching
(Green/Blue books, WRE, R internals, and other S4 resources), I haven't
figured out how to use .Data to point to a function, or more generally, how
to get numeric methods to work with my class. Any pointers or suggestions
would be greatly appreciated. Thanks!
Note: Im running R 2.15.1 on Windows XP from a binary.
Thanks,
Liz Sander
Microstrain
Williston, VT
setClass("range.vec",
representation(start = "numeric",
end = "numeric",
step = "numeric",
chunk = "numeric",
chunkpos = "numeric"),
contains="numeric" #so that it inherits from vector without assuming
logical data
)
setGeneric("set.chunk", function(x,...) standardGeneric("set.chunk"))
setMethod("set.chunk",
signature(x = "range.vec"),
function (x, chunksize=100, chunkpos=1)
{
#This function extracts a chunk of data from the range.vec object.
begin <- x@start + (chunkpos - 1)*x@step
end <- x@start + (chunkpos + chunksize - 2)*x@step
data <- seq(begin, end, x@step) #calculate values in data chunk
#get rid of out-of-bounds values
data[data > x@end] <- NA
x@chunk <- data
x@chunkpos <- chunkpos
return(x)
}
}
)
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