[R] Mode (statistics) in R?

[Marc Schwartz]

on 01/26/2009 07:28 AM Jason Rupert wrote:
> Hopefully this is a pretty simple question:
> �
> Is there a function in R that calculates the "mode" of a sample?�� That is, I would like to be able to determine the value that occurs the most frequently in a data set. 
> �
> I tried the default R "mode" function, but it appears to provide a storage type or something else.� 
> �
> I tried the RSeek and some R documentation that I downloaded, but nothing seems to mention calculating the "mode". 
> �
> Thanks again.

It depends upon the type of data you are dealing with.

If it is discrete, you can use table() to calculate frequencies and then
take the max:

set.seed(1)

tl <- table(sample(letters, 100, replace = TRUE))

> tl

a b c d e f g h i j k l m n o p q r s t u v w x y z
2 3 3 3 2 4 6 1 6 5 6 4 7 2 2 2 5 4 5 3 8 4 5 4 3 1

> tl[which.max(tl)]
u
8


Alternatively, if the data is continuous, then you will need to look at
some form of density estimation. There have been various discussions
over the years on how to go about doing this, but a simplistic approach
would be:

  set.seed(1)

  x <- rnorm(100)

  dx <- density(x)

  > dx$x[which.max(dx$y)]
  [1] 0.3294585


  # Review plot
  plot(dx)
  abline(v = dx$x[which.max(dx$y)])


See ?table, ?which.max and ?density

HTH,

Marc Schwartz