Euclidean distance is not a good measure in higher dimension: <a href="http:&#x2F;&#x2F;stats.stackexchange.com&#x2F;questions&#x2F;29627&#x2F;euclidean-distance-is-usually-not-good-for-sparse-data" rel="nofollow">http:&#x2F;&#x2F;stats.stackexchange.com&#x2F;questions&#x2F;29627&#x2F;euclidean-dis...</a>