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**CVEXHULL(***matrix***)**

where *matrix* is an *n* ×2 matrix of (*x*,*y*) points.

The argument for the CVEXHULL function is
an *n* ×2 matrix of (*x*,*y*) points.
The result matrix is an *n* ×1 matrix of indices.
The indices of points in the convex hull in counter-clockwise
order are returned as the first part of the result matrix,
and the negative of the indices of the internal points
are returned as the remaining elements of the result matrix.
Any points that lie on the convex hull but lie on a
line segment joining two other points on the convex
hull are not included as part of the convex hull.
The result matrix can be split into positive
and negative parts using the LOC function.
For example, the statements

z=cvexhull(x); c=z[loc(z>0),];yield the index vector for the convex hull.

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