38 lines
1.2 KiB
Rust
38 lines
1.2 KiB
Rust
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use nalgebra::*;
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pub struct Circle {
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pub center_x: f64,
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pub center_y: f64,
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pub radius: f64,
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}
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// construct the circle through the points given by the columns of `points`
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pub fn circ_thru(points: Matrix2x3<f64>) -> Option<Circle> {
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// build the matrix that maps the circle's coefficient vector to the
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// negative of the linear part of the circle's equation, evaluated at the
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// given points
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let neg_lin_part = stack![2.0*points.transpose(), Vector3::repeat(1.0)];
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// find the quadrdatic part of the circle's equation, evaluated at the given
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// points
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let quad_part = Vector3::from_iterator(
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points.column_iter().map(|v| v.dot(&v))
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);
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// find the circle's coefficient vector, and from there its center and
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// radius
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match neg_lin_part.lu().solve(&quad_part) {
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None => None,
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Some(coeffs) => {
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let center_x = coeffs[0];
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let center_y = coeffs[1];
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Some(Circle {
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center_x: center_x,
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center_y: center_y,
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radius: (
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coeffs[2] + center_x*center_x + center_y*center_y
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).sqrt(),
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})
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}
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}
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}
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