Reputation: 19756
I apologize for the vague title, could not think of anything short and specific.
I have a function foo
which performs some irrelevant calculation.
I have made the following methods.
foo.data.frame <- function(data, col1, col2){
return(data.frame(col1 = data[[col1]],
col2 = data[[col2]]))
}
foo.list <- function(data){
z <- unlist(data)
d <- names(z)
return(data.frame(col1 = z, col2 = d))
}
foo.character <- function(data){ #here data is a file address
if(file.exists(data)){
return(read.csv(data, row.names = 1))
}
}
some data:
df <- data.frame(col1 = letters[1:10],
col2 = 1:10)
lis <- as.list(df$col2)
names(lis) <- df$col1
write.csv(df, "df.csv")
These functions perform:
foo.data.frame(df, "col1", "col2"),
foo.list(lis)
foo.character("df.csv")
I am struggling to create a method which will take vectors as input for col1
and col2
:
foo.??? <- (data = NULL, col1, col2){
return(data.frame(col1, col2))
}
which will be used like this:
foo(col1 = df$col1, col2 = df$col2)
This can be
foo.default
or not
How should I go about this?
Do note that this is quite easy to do with "poor mans S3" (when all these functions are inside one, and by using an if-then-else clause to direct the object of the appropriate class to the appropriate method.
Upvotes: 4
Views: 213
Reputation: 270448
You will need to handle that in the foo
generic. For example,
foo.missing <- function(col1, col2) {
data.frame(col1 = col1, col2 = col2)
}
foo <- function(data, ...) {
if (missing(data) || is.null(data)) foo.missing(...)
else UseMethod("foo")
}
# test
foo(col1 = df$col1, col2 = df$col2)
foo(df, "col1", "col2"),
foo(lis)
foo("df.csv")
Upvotes: 3