Adding frequency column to each observation-CodePudding

everyone! Here's the problem , I have this dataset and I need to add a column with the frequency of each pet, I don't want a new dataframe with the statistics. See, dog and cat appears 6 time each, I need a column with value of 6 beside each dog and cat. Then I'll be able to make relational studies, which is why creating a new dataframe with summary is not an option

   id    answer
   <chr> <chr> 
 1 1     cat   
 2 1     dog   
 3 2     bird  
 4 3     cat   
 5 3     dog   
 6 3     fish  
 7 4     dog   
 8 5     turtle
 9 6     cat   
10 7     cat   
11 7     fish  
12 7     dog   
13 7     cat   
14 8     dog   
15 8     cat   
16 9     bird  
17 9     dog

by the end, it should look like this:

CodePudding user response：

Use add_count from dplyr package with the name argument:

library(dplyr)

df %>% 
  add_count(answer, name = "freq")

   id answer freq
1   1    cat    6
2   1    dog    6
3   2   bird    2
4   3    cat    6
5   3    dog    6
6   3   fish    2
7   4    dog    6
8   5 turtle    1
9   6    cat    6
10  7    cat    6
11  7   fish    2
12  7    dog    6
13  7    cat    6
14  8    dog    6
15  8    cat    6
16  9   bird    2
17  9    dog    6

CodePudding user response：

Using data.table you can group by frequency with .N

library(data.table)
your_table = as.data.table(your_table)
your_table[,freq := .N, by = answer]

#     id answer freq
#  1:  1    cat    6
#  2:  1    dog    6
#  3:  2   bird    2
#  4:  3    cat    6
#  5:  3    dog    6
#  6:  3   fish    2
#  7:  4    dog    6
#  8:  5 turtle    1
#  9:  6    cat    6
# 10:  7    cat    6
# 11:  7   fish    2
# 12:  7    dog    6
# 13:  7    cat    6
# 14:  8    dog    6
# 15:  8    cat    6
# 16:  9   bird    2
# 17:  9    dog    6