如何在 R 中使用 for 循环成对显示数字

Question

I am trying to use for loop for my R shiny app which is more complex than just displaying the numbers and characters. Hence, I have written a much simpler version here. Does anyone know how to display the following output using for loop?

"1,a"
"2,b"
"3,c"

So I have tried using the codes below:

for(i in 1:3) {
  for(j in c("a","b","c")) {
    
    print(paste(i,j,sep = ","))
  }}

However, it produces this output:

[1] "1,a"
[1] "1,b"
[1] "1,c"
[1] "2,a"
[1] "2,b"
[1] "2,c"
[1] "3,a"
[1] "3,b"
[1] "3,c"

Can anyone help me with this? Thanks!

Answer 1

You probably only need one index i .

for(i in 1:3) {
  print(paste(i, c("a","b","c")[i], sep = ","))
}
# [1] "1,a"
# [1] "2,b"
# [1] "3,c"

Answer 2

Unless you have a specific reason to be using one this is not a task best accomplished with a for loop. You can take advantage of the fact that paste is vectorised and do this:

paste(1:3, letters[1:3], sep = ",")

The sep argument to the paste function permits you to stitch together 2 vectors with a given string.