CODEWITHSUNDEEP
rcountsequence
Nicole Leitner
Nicole Leitner

Reputation: 11

Count number of times a particular value follows another particular value for each column in a data frame

I would like to create a table or a new data frame that displays, for each row in the original data frame, how many times a specific value precedes another specific value. For example, if I have the following data frame:

x <- data.frame("Red" = c("a", "b", "a", "a", "c", "d"), "Blue" = c("b", "a", "b", "a", "b", "a"), "Green" = c("a", "a", "b", "a", "b", "a"))

and I want to know, for each color (Red, Blue, and Green) how many times the sequence "b", "a" occurs (i.e., how many times b precedes a in the sequence).

The correct answer would look something like this:

     Color ba
1   Red  1
2  Blue  3
3 Green  2

Upvotes: 0

Views: 45

Answers (1)

Fred
Fred

Reputation: 420

here is one solution using stringr

library(stringr)

count_pair <- function(x, pattern) {
   p <- paste(pattern, collapse = "")
   s <- paste(x, collapse = "")
   str_count(s, pattern = p)
}

z <- apply(x, 2, count_pair, pattern = c("b", "a"))
# Red  Blue Green 
# 1     3     2 

# if you want the output in form of a data.frame you could run:
df <- as.data.frame(as.table(z))

#    Var1 Freq
# 1   Red    1
# 2  Blue    3
# 3 Green    2

Upvotes: 1

Related Questions