I'm trying to write a generic function that calls different methods depending on the structure of the argument, but not the exact type of its contents. For example, the function 'nan2last' below works for a numeric vector but not for a vector of Date objects. Is there any way to make it work on any vector?
setGeneric("nan2last", function(x) { standardGeneric("nan2last") })
setMethod(nan2last, "vector",
function(x) {
naLocs <- (1:length(x))[is.na(x)]
if (length(naLocs) == 0)
return (x)
naLocs <- naLocs[naLocs>1]
for (i in 1:length(naLocs)) {
x[naLocs[i]] <- x[naLocs[i]-1]
}
return(x)
})
## Works
x <- 1:10;
x[sample(10,3)] <- NA
print(cbind(x, nan2last(x)))
## Doesn't work
x <- seq(as.Date("2011-01-01"), as.Date("2011-01-31"), "days")
x[sample(length(x), 5)] <- NA
nan2last(x)
Thanks.
- Elliot
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