BoundingBall

BoundingBall [/F/Z] scatterWave

The BoundingBall operation calculates a bounding circle or the bounding sphere for a set of scatter points. The operation accepts 2D waves that have two, three or more columns; data in the additional columns are ignored.

When scatterWave consists of two columns the operation computes the bounding circle. Otherwise it computes the bounding 3D sphere.

Parameters

scatterWave is a two-dimensional wave with X coordinates in column 0, Y in column 1, and optional Z coordinates in column 2.

Flags

/F	This flag applies to 3D scatter only. It uses an algorithm from "An Efficient Bounding Sphere" by Jack Ritter originally from Graphics Gems. Unfortunately it does not give an accurate bounding ball but something that is sufficiently large. This algorithm is less accurate but it produces a ball which is sufficiently large to contain all the points.
/Z	No error reporting.

Details

The center and radius of the bounding sphere are stored in the variables: V_CenterX, V_CenterY, V_CenterZ, and V_Radius.

If you are not using the /F flag, the operation also accepts a 2 column wave consisting of x,y pairs for calculating the center and radius of a bounding circle in the plane.

Example

Make/N=(33,2) ddd=enoise(4)	// Create random data
BoundingBall ddd
Display ddd[][1] vs ddd[][0]
ModifyGraph mode=3
Make/n=360 xxx,yyy
yyy=v_centerY+V_radius*cos(p*2*pi/360)
xxx=v_centerX+V_radius*sin(p*2*pi/360)
AppendToGraph yyy vs xxx

References

Glassner, Andrew S. , (Ed.), "Graphics Gems", 864 pp., Morgan Kaufmann Publishers, 1990.