CIR_3PNT

The CIR_3PNT procedure returns the radius and center of a circle, given 3 points on the circle. This is analogous to finding the circumradius and circumcircle of a triangle; the center of the circumcircle is the point at which the three perpendicular bisectors of the triangle formed by the points meet.

This routine is written in the IDL language. Its source code can be found in the file


cir_3pnt.pro

in the

lib

subdirectory of the IDL distribution.

Arguments

X

A three-element vector containing the X-coordinates of the points.

Y

A three-element vector containing the Y-coordinates of the points.

R

A named variable that will contain the radius of the circle. The procedure returns 0.0 if the points are co-linear.

X0

A named variable that will contain the X-coordinate of the center of the circle. The procedure returns 0.0 if the points are co-linear.

Y0

A named variable that will contain the Y-coordinate of the center of the circle. The procedure returns 0.0 if the points are co-linear.

Example

X = [1.0, 2.0, 3.0]

Y = [1.0, 2.0, 1.0]

CIR_3PNT, X, Y, R, X0, Y0

PRINT, 'The radius is: ', R

PRINT, 'The center of the circle is at: ', X0, Y0

CIR_3PNT

Calling Sequence

Arguments

X

Y

R

X0

A named variable that will contain the X-coordinate of the center of the circle. The procedure returns 0.0 if the points are co-linear.

Y0

Example

See Also