Identify the center of a small circle based on three points of a sphere

Identify the center of a small circle based on three points of a sphere

Usage

sc_center(x, origin = c(0, 0, 0), output = "polar")

Arguments

x

A matrix of 3 points, either polar longitude and latitude coordinates, or XYZ Cartesian coordinates.

origin

The origin of the sphere.

output

If set to "polar" then the function will return the longitude and latitude of the small circle center.

Value

A list with two elements, the center o the small circle and the surface radius of the small circle.

Examples

# generate 3 points on a sphere
set.seed(2)
ps <- icosa::rpsphere(3, output="polar")
small <- sc_center(x=ps)
circle<- sc_shape(x=small$center, r=small$r, output="polar")

plot(NULL, NULL, xlim=c(-180, 180), ylim=c(-90, 90))
points(ps, col="red", pch=3, cex=4)
points(small$center, col="blue", pch=16)
points(circle, col="green", pch=16)