[R] mahalanobis distance

Ekin Akoglu ekin at ims.metu.edu.tr
Mon Jul 20 22:47:35 CEST 2009


Thank you..this is what i needed...

Rolf Turner wrote:
>
> On 21/07/2009, at 7:57 AM, Michael Knudsen wrote:
>
>> On Mon, Jul 20, 2009 at 9:37 PM, ekinakoglu<ekin at ims.metu.edu.tr> wrote:
>>
>>> Could you please help me with a pseudo matrix of 4x4
>>> that is gonna work with mahalanobis?
>
>     Please speak English.  ``gonna'' is not appropriate
>     for written communication.
>
>> Hmmm ... I have been trying some different matrices myself now, but I
>> keep getting the same error. Even if det(S) is very far from zero.
>> Maybe I just don't get the point of the mahalanobis() function in R.
>> It looks quite weird to me :-(
>
> Huh?
>
> Try:
>
> > set.seed(42)
> > X <- matrix(rnorm(100),25,4)
> > S <- var(X)
> > x <- rnorm(4)
> > mahalanobis(x,rep(1,4),S)
> [1] 6.082543
>
>     cheers,
>
>         Rolf Turner
>
>
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