Re: [R] var on a vector

[Matthias Kohl]

[EMAIL PROTECTED] schrieb:

Hello

I am an "R" newbie. I have a problem with computing a variance on a vector.

 

data(cars)
variance <- function (x) mean(x^2)-mean(x)^2;
variance(cars[,1])
   

[1] 27.4
 

var(cars[,1])
   

[1] 27.95918

What did I assume/understand wrong ?

TIA

 

Hello,

help(var) says:

The denominator n - 1 is used which gives an unbiased estimator of
the (co)variance for i.i.d. observations.
Try:
n <- length(cars[,1])
var(cars[,1])*(n-1)/n
Matthias Kohl

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