Summary for mode of a data set

Dear Spencer:

In the following example, your code doesn't pick up the local mode at 5.

x2 <- c(1,1,2,3,3,3,3,5,5,5)
modes(x2)

[1] 1 3

In this example, it gives a mode at 7, which is incorrect.

x2 <- c(1,1,2,3,3,3,3,5,5,5,6,7)
modes(x2)

[1] 1 3 7

Ravi.

----- Original Message -----
From: Spencer Graves <spencer.graves at pdf.com>
Date: Monday, June 23, 2003 2:53 pm
Subject: Re: [R] Summary for mode of a data set

Your "mode1" function will identify multiple modes only if they 
have the 
same number of observations.  Consider the following:

x2 <- c(2, 1,1, 3,3,3)
mode1(x2)

[1] 3

Here, "mode1" did not identify the local mode at 1, because it had 
fewer 
observations than 3.  If you want the modes at both 1 and 3, then 
consider the following:

modes <- function(x){
xt <- table(x)
nt <- length(xt)
sel <- c(xt[-nt]>=xt[-1], T)&c(T, xt[-1]>=xt[-nt])
as.numeric(names(xt[sel]))
}

modes(x2)

[1] 1 3

hth.  spencer graves

Erin Hodgess wrote:

Dear R People:

thank you for the many helpful sets of code that I received!!!

I combined several of the concepts for the following function:

mode1

function(x) {

       y <- rle(sort(x))

       z <- y$values[y$lengths==max(y$lengths)]

       return(z)

}

xm

[1] 22 15 10 30 25 26  2 17 28  2 24  6 26 24  5 22 20 14

mode1(xm)

[1]  2 22 24 26



This will pick up multiple modes.

Again thanks to all who helped!

Sincerely,
Erin 
mailto: hodgess at uhddx.01.dt.uh.edu