How to find the statistical mode?

Question

In R, mean() and median() are standard functions which do what you\'d expect. mode() tells you the internal storage mode of the objec

Answer 1

Another possible solution:

Mode <- function(x) {
    if (is.numeric(x)) {
        x_table <- table(x)
        return(as.numeric(names(x_table)[which.max(x_table)]))
    }
}

Usage:

set.seed(100)
v <- sample(x = 1:100, size = 1000000, replace = TRUE)
system.time(Mode(v))

Output:

   user  system elapsed 
   0.32    0.00    0.31 

Answer 2

Could try the following function:

1. transform numeric values into factor
2. use summary() to gain the frequency table
3. return mode the index whose frequency is the largest
4. transform factor back to numeric even there are more than 1 mode, this function works well!

mode <- function(x){
  y <- as.factor(x)
  freq <- summary(y)
  mode <- names(freq)[freq[names(freq)] == max(freq)]
  as.numeric(mode)
}

Answer 3

This hack should work fine. Gives you the value as well as the count of mode:

Mode <- function(x){
a = table(x) # x is a vector
return(a[which.max(a)])
}

Answer 4

While I like Ken Williams simple function, I would like to retrieve the multiple modes if they exist. With that in mind, I use the following function which returns a list of the modes if multiple or the single.

rmode <- function(x) {
  x <- sort(x)  
  u <- unique(x)
  y <- lapply(u, function(y) length(x[x==y]))
  u[which( unlist(y) == max(unlist(y)) )]
} 

Answer 5

The following function comes in three forms:

method = "mode" [default]: calculates the mode for a unimodal vector, else returns an NA
method = "nmodes": calculates the number of modes in the vector
method = "modes": lists all the modes for a unimodal or polymodal vector

modeav <- function (x, method = "mode", na.rm = FALSE)
{
  x <- unlist(x)
  if (na.rm)
    x <- x[!is.na(x)]
  u <- unique(x)
  n <- length(u)
  #get frequencies of each of the unique values in the vector
  frequencies <- rep(0, n)
  for (i in seq_len(n)) {
    if (is.na(u[i])) {
      frequencies[i] <- sum(is.na(x))
    }
    else {
      frequencies[i] <- sum(x == u[i], na.rm = TRUE)
    }
  }
  #mode if a unimodal vector, else NA
  if (method == "mode" | is.na(method) | method == "")
  {return(ifelse(length(frequencies[frequencies==max(frequencies)])>1,NA,u[which.max(frequencies)]))}
  #number of modes
  if(method == "nmode" | method == "nmodes")
  {return(length(frequencies[frequencies==max(frequencies)]))}
  #list of all modes
  if (method == "modes" | method == "modevalues")
  {return(u[which(frequencies==max(frequencies), arr.ind = FALSE, useNames = FALSE)])}  
  #error trap the method
  warning("Warning: method not recognised.  Valid methods are 'mode' [default], 'nmodes' and 'modes'")
  return()
}

Answer 6

This works pretty fine

> a<-c(1,1,2,2,3,3,4,4,5)
> names(table(a))[table(a)==max(table(a))]