[R] Mahalanobis distance

From: yoo hoo <freesuccess2001_at_yahoo.com>
Date: Tue, 22 Jun 2010 14:41:23 -0700 (PDT)

I am a new R user. i have a question about Mahalanobis distance.actually i have 300 rows and 7 columns. columns are different measurements, 300 rows are genes. since genes can classify into 4 categories. i used dist() with euclidean distance and cmdscale to do MDS plot. but find out Mahalanobis distance may be better. how do i use Mahalanobis() to generate similar dist object which i can use MDS plot? second question is if should i calculate mean for every categories for every measurement first and do 4*4 distance matrix, or i should calculate pairwise distance first and then find category means since i only care about relative position of 4 categories in MDS plot. Thank you very much.

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