Order column with integers separated by "-" in R [duplicate] - r

Question

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Order a "mixed" vector (numbers with letters)
(1 answer)
Closed 4 years ago.
I would like to order a column containing characters like this:
K3SG1-105-1051-1
However, using the arrange function will result in this:
K3SG1-105-1051-1
K3SG1-105-1051-10
K3SG1-105-1051-100
K3SG1-105-1051-1000
Instead of what I want:
K3SG1-105-1051-1
K3SG1-105-1051-2
K3SG1-105-1051-3
K3SG1-105-1051-4
Thanks in advance.

Answer 1

Here is a possibility using tidyr::separate and dplyr:
# Sample data
df <- data.frame(id = paste0("K3SG1-105-1051-", seq(1:10)));
# Using separate
df %>%
separate(id, into = paste0("id", 1:4), sep = "-", remove = FALSE) %>%
arrange(as.numeric(id4)) %>%
select(id);
# id
#1 K3SG1-105-1051-1
#2 K3SG1-105-1051-2
#3 K3SG1-105-1051-3
#4 K3SG1-105-1051-4
#5 K3SG1-105-1051-5
#6 K3SG1-105-1051-6
#7 K3SG1-105-1051-7
#8 K3SG1-105-1051-8
#9 K3SG1-105-1051-9
#10 K3SG1-105-1051-10
Explanation: Split column id into four separate columns based on "-" as separator; arrange rows based on the fourth column entries, which are converted to numeric to ensure proper ordering.

Answer 2

Data
I created the following example data for this answer:
(char_vec <- paste0("K3SG1-105-1051-", c(1:4, 10, 100, 1000)))
[1] "K3SG1-105-1051-1" "K3SG1-105-1051-2" "K3SG1-105-1051-3"
[4] "K3SG1-105-1051-4" "K3SG1-105-1051-10" "K3SG1-105-1051-100"
[7] "K3SG1-105-1051-1000"
Solution
char_vec[order(as.numeric(sub('.*-', '', char_vec)))]
[1] "K3SG1-105-1051-1" "K3SG1-105-1051-2" "K3SG1-105-1051-3"
[4] "K3SG1-105-1051-4" "K3SG1-105-1051-10" "K3SG1-105-1051-100"
[7] "K3SG1-105-1051-1000"
Explanation
sub('.*-', '', char_vec) gets just the last number characters in the vector, which we then convert to numeric and order to order char_vec.
If you order the characters 1, 2, and 10, the order is 1, 10, 2 because you're alphabetically ordering strings, not ordering numbers.