CODEWITHSUNDEEP
raggregatefrequency
Nata
Nata

Reputation: 171

How to find frequency of each class within a group in R?

I have the following data:

df <- read.table(text =
    "   id    country
    1   IT
    1   IT
    1   USA
    2   USA
    2   FR
    2   IT
    3   USA
    3   USA
    3   IT
    3   FR", header = T)

I need to find frequency of each country within every ID. So, the desired output is:

       id  IT  USA  FR
        1   2   1   0
        2   1   1   1
        3   1   2   1

I know how to calculate with count() the number of rows for each id but I don't know how to display by each country. Thanks for help!

Upvotes: 0

Views: 357

Answers (2)

sai saran
sai saran

Reputation: 757

it can be done with xtabs in simple way :

xtabs(~df$id+df$country) or 

xtabs(~df+country,data=df)

output:

     df$country
df$id FR IT USA
    1  0  2   1
    2  1  1   1
    3  1  1   2

Upvotes: 0

RLave
RLave

Reputation: 8374

With dplyr:

library(dplyr)
df %>% 
  group_by(id) %>%
  count(country) %>% # count having grouped by ids
  spread(country, n) # we spread the values, in order to have long format

# A tibble: 3 x 4
# Groups:   id [3]
     id    FR    IT   USA
  <int> <int> <int> <int>
1     1    NA     2     1
2     2     1     1     1
3     3     1     1     2

This if you want to replace NA with 0:

df %>% 
  group_by(id) %>%
  count(country) %>% 
  spread(country, n) %>% 
  mutate_each(funs(replace(., is.na(.), 0))) # mutate applied for all variables, where we find NA
# A tibble: 3 x 4
# Groups:   id [3]
     id    FR    IT   USA
  <int> <dbl> <dbl> <dbl>
1     1     0     2     1
2     2     1     1     1
3     3     1     1     2

Upvotes: 3

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