使用对数据框中的行进行迭代的函数将元素追加到列表中

Question

I'm trying to use a list like a python dict, which can be appended to every time a function is run. Ultimately I want to apply the function to every row in a data frame. I'm trying it out on some toy data:

foo <- vector(mode="list", length=2)
names(foo) <- c("Larry", "Bob")

myfun <- function(name, round, foo){
 foo[[name]] <<- c(foo[[name]], round)
}

This works when I run it separately over some data:

myfun("Larry", "R2", foo)
myfun("Larry", "R2", foo)
myfun("Bob", "R1", foo)
myfun("Larry", "R1", foo)

foo
$Larry
[1] "R2" "R2" "R1"

$Bob
[1] "R1"

But I can't get the function to work over a data frame:

datf <- data.frame(name = c("Larry", "Larry", "Bob", "Larry"),
                   round = c("R2", "R2", "R2", "R1"))
mapply(myfun, name=datf$name, round=datf$round, foo=foo)

This produces the following in the console (I'm not sure why?):

[1] 1 1 2 3

and the following in foo:

foo
$Larry
[1] 2

$Bob
[1] 3

My other thought was to try applying myfun() in a for loop:

for(row in 1:nrow(datf)){
  myfun(datf$name, datf$round, foo)
}

But this produces an error:

Error in foo[[name]] : no such index at level 2

Any insights would be appreciated!

Answer 1

A little better example of the function you're trying to run and the result would be helpful. I would think about using the dplyr::mutate function. Alternatively, if you're trying to just do something simple, I think you can just make a new column in the dataframe datf$new <- myfun(inputs)