I am new to R and for a homework assignment we have to extract the first elements of each column from a list to sum these up. My current code seems to work fine but it feels like I am not using the inhert R characteristics to efficiently work with the list. (Instead it feels like I'm just applying methods to deal with lists I learned in Java)
I have a list:
mylist <- list(points_ex1=c(15,18,12), points_ex2=c(9,16,8), points_ex3=c(83,95,39))
and I am trying to sum up the first/second/third value of each vector respectively. For the first column this would result in 15+9+83=107
Currently I am using two nested for loops to traverse the list and then appending each element to a temporary vector, who's sum is then appended to a vector of the total points.
total_points <- NULL #object to append total scores to
for (i in 1:3){
temp <- NULL #object to append points to
for (j in 1:3){
temp <- append(temp, mylist[[j]][i]) #appending the i-th element of each test score vector, before appending that sum
#to the total_points vector and continuing with the next row
}
total_points <- append(total_points, sum(temp))
}
This works as expected, but feels like it does not use any useful R characteristics (e.g. a function like sapply()). Are there any good options to improve this code?
As this is my first question here please do tell me if I am breaking any conventions/netequitte on this site! Thank you.
When list items all have the same length, it's usually easier to have them as a data frame. I would do
mylist |>
as.data.frame() |>
rowSums()
# [1] 107 129 59
If you don't want to rely on the list being convertible to a data frame, and instead want to extract the ith element of each item and sum them, then I would do it like this:
i = 1
sapply(mylist, "[", i) |> ## extract `i`th element
sum() ## and sum
# [1] 107
Which you could then repeat for whichever values of i you want.