Creating functions within a nested loop - r

Question

I was hoping to create a function with the if statements in the following code:
data <- data.frame(
id = c(1, 5, 6, 11, 15, 21),
intervention = c(2, 2, 2, 1, 1, 1),
death = c(0, 1, 0, 1, 0, 0)
)
test <- c()
for (i in data$id[which(data$intervention == 1)]) {
print(paste0("id = ", i, ": "))
for (j in data$id[which(data$intervention == 2)]) {
if (data$death[data$id == i] < data$death[data$id == j]) {
test <- c(test, -1)
} else if (data$death[data$id == i] > data$death[data$id == j]) {
test <- c(test, 1)
} else if (data$death[data$id == i] == data$death[data$id == j]) {
test <- c(test, 0)
}
}
print(test)
test <- c()
}
I had tried to do it as follows, however the code is not writing the result to the vector. However if I replaced the return with print, it would print it out. Would anyone have any suggestions on what I might be doing wrong? Many thanks!
first <- function () {
if(data$death[data$id == i]<data$death[data$id ==j]){
return (test <- c(test,-1))}
else if(data$death[data$id == i]>data$death[data$id == j]){
return (test <- c(test,1))}
else if(data$death[data$id == i]==data$death[data$id == j]){
return (test <- c(test,0))}
}
for (i in data$id[which(data$intervention == 1)]){
for (j in data$id[which(data$intervention == 2)]){
first()
}
test
}

Answer 1

The following function returns a list of the wanted vectors.
first <- function(data, interv1 = 1, interv2 = 2) {
inx <- which(data[["intervention"]] == interv1)
jnx <- which(data[["intervention"]] == interv2)
out <- lapply(inx, \(i) {
sapply(jnx, \(j) sign(data[["death"]][i] - data[["death"]][j]))
})
setNames(out, data[["id"]][inx])
}
first(data)
#> $`11`
#> [1] 1 0 1
#>
#> $`15`
#> [1] 0 -1 0
#>
#> $`21`
#> [1] 0 -1 0
Created on 2022-11-22 with reprex v2.0.2
You can then access the return values as
test <- first(data)
# any of the following extracts the 1st vector
test[['11']]
#> [1] 1 0 1
# notice the backticks
test$`11`
#> [1] 1 0 1
Created on 2022-11-22 with reprex v2.0.2