Dealing with ties using rank (R)

Question

I'm trying to create dummy variable for whether a child is first born, and one for if the child is second born. My data looks something like this

ID   MID   CMOB   CYRB      
1    1     1      1991
2    1     7      1989
3    2     1      1985
4    2     11     1985
5    2     9      1994
6    3     4      1992
7    4     2      1992
8    4     10     1983

With ID = child ID, MID = mother ID, CMOB = month of birth and CYRB = year of birth.

For the first born dummy I tried using this:

Identifiers_age <- Identifiers_age %>% group_by(MPUBID) 
                          %>% mutate(first = as.numeric(rank(CYRB) == 1))

But there doesn't seem to be a way of breaking ties by the rank of another columnn (clearly in this case the desired column being CMOB), whenever I try using the "ties.method" argument it tell me the input must be a character vector.

Am I missing something here?

score 4 · Accepted Answer · answered Aug 06 '16 at 13:54

order might be more convenient to use here, from ?order:

order returns a permutation which rearranges its first argument into ascending or descending order, breaking ties by further arguments.

Identifiers_age <- Identifiers_age %>% group_by(MID) %>% 
                   mutate(first = as.numeric(order(CYRB, CMOB) == 1))
Identifiers_age

#Source: local data frame [8 x 5]
#Groups: MID [4]

#     ID   MID  CMOB  CYRB first
#  <int> <int> <int> <int> <dbl>
#1     1     1     1  1991     0
#2     2     1     7  1989     1
#3     3     2     1  1985     1
#4     4     2    11  1985     0
#5     5     2     9  1994     0
#6     6     3     4  1992     1
#7     7     4     2  1992     0
#8     8     4    10  1983     1

score 1 · Answer 2 · answered Aug 06 '16 at 15:13

If we still want to use rank, we can convert the 'CYRB', 'CMOB' in to 'Date', apply rank on it and the get the binary output based on the logical vector

Identifiers_age %>%
         group_by(MID) %>% 
         mutate(first = as.integer(rank(as.Date(paste(CYRB, CMOB, 1,
                  sep="-"), "%Y-%m-%d"))==1))
#     ID   MID  CMOB  CYRB first
#  <int> <int> <int> <int> <int>
#1     1     1     1  1991     0
#2     2     1     7  1989     1
#3     3     2     1  1985     1
#4     4     2    11  1985     0
#5     5     2     9  1994     0
#6     6     3     4  1992     1
#7     7     4     2  1992     0
#8     8     4    10  1983     1

Or we can use arithmetic to do this with rank

Identifiers_age %>% 
         group_by(MID) %>%
         mutate(first = as.integer(rank(CYRB + CMOB/12)==1))
#     ID   MID  CMOB  CYRB first
#   <int> <int> <int> <int> <int>
#1     1     1     1  1991     0
#2     2     1     7  1989     1
#3     3     2     1  1985     1
#4     4     2    11  1985     0
#5     5     2     9  1994     0
#6     6     3     4  1992     1
#7     7     4     2  1992     0
#8     8     4    10  1983     1

Dealing with ties using rank (R)

2 Answers2