graph laplacian of the adjacency graph
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Calculate the graph laplacian of the adjacency graph of data set DATA.
L = laplacian(DATA, TYPE, PARAM)
DATA - NxK matrix. Data points are rows.
TYPE - string 'nn' or string 'epsballs'
PARAM - integer if TYPE='nn', real number if TYPE='epsballs'
Returns: L, sparse symmetric NxN matrix
Example:
L = laplacian(X,'nn',6)
L contains the Laplacian of the graph obtained from connecting
each point of the data set to its 6 nearest neigbours.