在 scipy 的 ConvexHull 中，“区域"是指什么?措施? [英] In scipy's ConvexHull, what does "area" measure?

问题描述

scipy ConvexHull 中area"属性的值(参见 http://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.ConvexHull.html) 对象似乎不是(我理解的)区域凸包.另一方面，体积"的值似乎确实是凸包的面积.

The value of the "area" attribute in scipy ConvexHull (see http://docs.scipy.org/doc/scipy/reference/generated/scipy.spatial.ConvexHull.html) object does not seem to be (what I understand to be) the area of the convex hull. On the other hand, the value of "volume" does seem to be the area of the convex hull.

from scipy.spatial import ConvexHull
import numpy

points = numpy.array([[-1,-1], [1,1], [-1, 1], [1,-1]])
hull = ConvexHull(points)

print("Volume is %2.2f" % hull.volume) # Prints 4.00
print("Area is %2.2f" % hull.area) # Prints 8.00

在上面的例子中，我期望 4 个点的凸包面积为 4.0.这就是音量".那么区域"给了我们什么?

In the above example, I expect the area of the convex hull of the 4 points to be 4.0. That's what the "volume" is. What then does "area" give us?

推荐答案

体积和面积是 3d 概念，但您的数据是 2d - 一个 2x2 的正方形.它的面积是 4，周长是 8(2d 对应物).

Volume and area are 3d concepts, but your data is 2d - a 2x2 square. Its area is 4, and perimeter is 8 (the 2d counterparts).

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