将频率分配为 r 中的新列

Question

Let's say I have the following string:

a <- c("a", "b", "c", "b", "a", "a", "e")
b <- table(a)

b gives me the frequency of every element in a. How do I create a dataframe with two columns, the first column is a and in the second I have the frequency of each element?

The output should look like this:

f <- c(3, 2, 1, 2, 3, 3, 1)
output <- data.frame(a,f)

Thank you very much in advance!

Answer 1

We can use add_count to create a new column

library(tibble)
library(dplyr)
tibble(a) %>% 
     add_count(a)

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Or in base R with ave

data.frame(a, freq = ave(seq_along(a), a, FUN = length))

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Or if it needs to be from 'b', do the match with the names of 'b' and the vector 'a' to expand the table output and then convert the table object to data.frame with as.data.frame

as.data.frame(b[a])
#  a Freq
#1 a    3
#2 b    2
#3 c    1
#4 b    2
#5 a    3
#6 a    3
#7 e    1

Answer 2

Using merge:

merge(as.data.frame(a), as.data.frame(table(a)))

#  a Freq
#1 a    3
#2 a    3
#3 a    3
#4 b    2
#5 b    2
#6 c    1
#7 e    1