count the most occurring digits in R-CodePudding

I am doing this practice problem that wants me to write a function that can calculate the digits that occur the most number of times in the array. The example is input x= c(25, 2, 3, 57, 38, 41), and the return value is 2, 3, 5, since these numbers 2, 3 and 5 all occurs 2 times which is the most.

I am new to programming and I have no clue that how I can approach this.

CodePudding user response：

One approach would look something like this, although I am sure there are more efficient approaches:

my_vector <- c(25, 2, 3, 57, 38, 41)

# function to evaluate the number of times a certain digit occurrs
digit_occurrence <- function(vector) {
  
  # collape vector to a single string without commas
  x <- paste(vector, sep = '', collapse = '')

  # create empty vector
  digit <- c()

  # loop over each unique digit and store its occurrence
  for(i in paste(as.character(0:9))) {
    digit[i] <- lengths(regmatches(x, gregexpr(i, x)))
  }

  digit

}

> digit_occurrence(my_vector)
0 1 2 3 4 5 6 7 8 9 
0 1 2 2 1 2 0 1 1 0

CodePudding user response：

This could be another option for you:

fn <- function(x) {

  # First We separate every single digit in each element but we need to turn
  # the each element into character string beforehand. We then use do.call 
  # function to apply c function on every element of the resulting list to 
  # flatten the list to a vector
  digits <- do.call(c, sapply(x, function(y) strsplit(as.character(y), "")))

  # Then we turn the resulting character vector into numeric
  digits_num <- as.numeric(digits)
  
  # In the end we calculate the frequencies and sort the in decreasing order
  most_freq <- sort(table(digits_num), decreasing = TRUE)
  most_freq
}

fn(x)

digits_num
2 3 5 1 4 7 8 
2 2 2 1 1 1 1