For this problem, we will use the k-NN algorithm—k here means that we will look at k-closest neighbors. Given a white point, it will be classified as an area of water if the majority of its k-closest neighbors are in an area of water and classified as land if the majority of its k-closest neighbors are an area of land. We will use the Euclidean metric for the distance: given two points, X=[x0,x1] and Y=[y0,y1], their Euclidean distance is defined as dEuclidean = sqrt((x0-y0)2+(x1-y1)2).

The Euclidean distance is the most common metric. Given two points on a piece of paper, their Euclidean distance is just the length between the two points, as measured by a ruler, as shown in the following diagram:

To apply the k-NN algorithm to ...

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