将序列转换为R中的ODD或偶数序列

Question

If I have a sequence of numbers within a dataframe - is it possible to create a new column that follows the sequence but shows only the odd or even - heres an example:

SEQ      ODDSEQ   EVENSEQ
1        1        2
1        1        2
1        1        2
2        3        4
2        3        4
2        3        4
3        5        6
3        5        6
3        5        6
4        7        8
4        7        8
4        7        8

So SEQ is what I have right now...a repeated sequence, I'd like to create columns 2 & 3..? I know Modulo is somehow involved bu I can quite get it.

Any ideas..? Paul

Answer 1

Assuming that we need a general method

library(dplyr)
df1 %>% 
     mutate(ODDSEQ = seq(1, length.out= n_distinct(SEQ), by = 2)[match(SEQ, unique(SEQ))],
           EVENSEQ = seq(2, length.out = n_distinct(SEQ), by = 2)[match(SEQ, unique(SEQ))])
#    SEQ ODDSEQ EVENSEQ
#1    1      1       2
#2    1      1       2
#3    1      1       2
#4    2      3       4
#5    2      3       4
#6    2      3       4
#7    3      5       6
#8    3      5       6
#9    3      5       6
#10   4      7       8
#11   4      7       8
#12   4      7       8