Create a variable capturing the most frequent occurence by group

Question

Define:

df1 <-data.frame(
id=c(rep(1,3),rep(2,3)),
v1=as.character(c(\"a\",\"b\",\"b\",rep(\"c\",3)))
)

s.t.

> df1
           


        

Answer 1

Another way consists of using tidyverse functions:

• grouping first, using group_by(), and counting the occurrence of the second variable using tally()
• arranging by the number of occurrences with arrange()
• summarizing and picking out the first row with summarize() and first()

Therefore:

df1 %>%
group_by(id, v1) %>%
tally() %>%
arrange(id, desc(n)) %>%
summarize(freq = first(v1))

This will give you just the mapping (which I find cleaner):

# A tibble: 2 x 2
     id   freq
   
1     1      b
2     2      c

You can then left_join your original data frame with that table.