Can I extract a variable name from a vector using a for loop?

Question

I am practicing loops and trying to figure out how to print ___ is a good friend if their number is odd (through an assigned number in a vector) - why won't it print the names of the people in the vector who are coded as odd numbers?

B_list <- c(Bob=1, Bill=2, Buddy=3) # create character vector

phrase <- "is a good friend"

for (i in B_list){
    if((i %% 2) != 0)
        print(paste(names(i),phrase))
}

Output:

[1] " is a good friend"
[1] " is a good friend"

Should have been names(B_list)[i]. You tried to get the name of 1. It doesn't have a name, it's just a number. You should have gotten an error and then searched SO with selected parts of the error message. — IRTFM
– IRTFM, Commented Jul 19, 2022 at 2:20

Sercan · Accepted Answer · 2022-07-19 02:01:42Z

1

names(listName[i]) should be used to get the name of the item in the list, and listName[[i]] should be used to get the value of the item in the list.

B_list <- c(Bob=1, Bill=2, Buddy=3)

phrase <- "is a good friend"

for (i in B_list) {
    if((i %% 2) != 0) {
        print(paste(names(B_list[i]), phrase))
        
        print(paste("Name: ", names(B_list[i])))
        print(paste("Value: ", B_list[[i]]))
    }
}

The output:

[1] "Bob is a good friend"
[1] "Name:  Bob"
[1] "Value:  1"
[1] "Buddy is a good friend"
[1] "Name:  Buddy"
[1] "Value:  3"

edited Jul 19, 2022 at 2:01

answered Jul 19, 2022 at 1:52

Sercan

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1 Comment

R_User_23 Over a year ago

Incredible! Thanks. Loops are new to me so very grateful for the help.

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